[Mac] [Reland] On the Touch Bar, use individual back/forward buttons instead of semented control.

This relands the original change, fixing a use-after-free when
BrowserWindowDefaultTouchBar outlives its profile.

Original change's description:

> This is a design tweak which also enables the back and forward buttons
> to be placed separately. Existing customized Touch Bars which contain
> the grouped item still work; see the code comment for details.
>
> I used Cocoa bindings for the buttons' enabled states instead of holding
> pointers to them because I initially thought that the Touch Bar might allow the
> group and individual buttons to coexist. Turns out no, but I kept the KVO
> implementation because I like it.
>
> It also includes a couple of other changes that came up while writing
> this patch and during code review:
>
> - The unit tests no longer look for a hard-coded list of items in a
>   specific order. Instead, they verify that BrowserWindowDefaultTouchBar
>   can create the items it claims to be able to create, and that no
>   known-valid identifiers have stopped working.
>
> - BrowserWindowDefaultTouchBar returns nil if it doesn't know about an
>   identifier, instead of returning an empty Touch Bar item.
>
> Bug: 937935
> Change-Id: I8cdc6347bc667b0a24fa24fe2c6a56661747ac98
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1534238
> Commit-Queue: Sidney San Martín <sdy@chromium.org>
> Reviewed-by: Leonard Grey <lgrey@chromium.org>
> Auto-Submit: Sidney San Martín <sdy@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#649899}

Bug: 937935, 945772
Change-Id: I77bf9b6d14bef875f271f8fbd4468e6cdc30434e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1568846
Commit-Queue: Sidney San Martín <sdy@chromium.org>
Reviewed-by: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#651851}

chrome/browser/ui/cocoa/touchbar/browser_window_default_touch_bar.h

@@ -14,10 +14,6 @@ class BookmarkTabHelperObserver;
 class Browser;
 @class BrowserWindowTouchBarController;
 
-namespace content {
-class WebContents;
-}
-
 // Provides a default touch bar for the browser window. This class implements
 // the NSTouchBarDelegate and handles the items in the touch bar.
 API_AVAILABLE(macos(10.12.2))
@@ -29,18 +25,18 @@ API_AVAILABLE(macos(10.12.2))
 // True if the current page is starred. Used by star touch bar button.
 @property(nonatomic, assign) BOOL isStarred;
 
-// Designated initializer.
-- (instancetype)initWithBrowser:(Browser*)browser
-                     controller:(BrowserWindowTouchBarController*)controller;
+// True if the back button is enabled.
+@property(nonatomic, assign) BOOL canGoBack;
 
-// Creates and returns a touch bar for the browser window.
-- (NSTouchBar*)makeTouchBar;
+// True if the forward button is enabled.
+@property(nonatomic, assign) BOOL canGoForward;
+
+@property(nonatomic, assign) BrowserWindowTouchBarController* controller;
 
-- (void)updateWebContents:(content::WebContents*)contents;
+@property(nonatomic) Browser* browser;
 
-// Updates the back/forward button. Called when creating the touch bar or when
-// the back and forward commands have changed.
-- (void)updateBackForwardControl;
+// Creates and returns a touch bar for the browser window.
+- (NSTouchBar*)makeTouchBar;
 
 - (BrowserWindowTouchBarController*)controller;
 
@@ -49,6 +45,11 @@ API_AVAILABLE(macos(10.12.2))
 // Private methods exposed for testing.
 @interface BrowserWindowDefaultTouchBar (ExposedForTesting)
 
+@property(readonly, class) NSString* reloadOrStopItemIdentifier;
+@property(readonly, class) NSString* backItemIdentifier;
+@property(readonly, class) NSString* forwardItemIdentifier;
+@property(readonly, class) NSString* fullscreenOriginItemIdentifier;
+
 // Updates the reload/stop button. Called when creating the touch bar or the
 // page load state has been updated.
 - (void)updateReloadStopButton;
@@ -56,10 +57,6 @@ API_AVAILABLE(macos(10.12.2))
 // Returns the reload/stop button on the touch bar. Creates it if it's null.
 - (NSButton*)reloadStopButton;
 
-// Returns the back/forward segmented control on the touch bar. Creates it if
-// it's null.
-- (NSSegmentedControl*)backForwardControl;
-
 // Returns the bridge object that BrowserWindowDefaultTouchBar uses to receive
 // notifications.
 - (BookmarkTabHelperObserver*)bookmarkTabObserver;

chrome/browser/ui/cocoa/touchbar/browser_window_default_touch_bar.mm

@@ -13,6 +13,7 @@
 #include "base/strings/sys_string_conversions.h"
 #include "chrome/app/chrome_command_ids.h"
 #include "chrome/app/vector_icons/vector_icons.h"
+#include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/command_observer.h"
 #include "chrome/browser/command_updater.h"
 #include "chrome/browser/profiles/profile.h"
@@ -32,6 +33,7 @@
 #include "components/strings/grit/components_strings.h"
 #include "components/url_formatter/url_formatter.h"
 #include "components/vector_icons/vector_icons.h"
+#include "content/public/browser/notification_service.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_contents_observer.h"
 #import "skia/ext/skia_utils_mac.h"
@@ -51,7 +53,8 @@ NSString* const kBrowserWindowTouchBarId = @"browser-window";
 NSString* const kTabFullscreenTouchBarId = @"tab-fullscreen";
 
 // Touch bar items identifiers.
-NSString* const kBackForwardTouchId = @"BACK-FWD";
+NSString* const kBackTouchId = @"BACK";
+NSString* const kForwardTouchId = @"FORWARD";
 NSString* const kReloadOrStopTouchId = @"RELOAD-STOP";
 NSString* const kHomeTouchId = @"HOME";
 NSString* const kSearchTouchId = @"SEARCH";
@@ -59,9 +62,11 @@ NSString* const kStarTouchId = @"BOOKMARK";
 NSString* const kNewTabTouchId = @"NEW-TAB";
 NSString* const kFullscreenOriginLabelTouchId = @"FULLSCREEN-ORIGIN-LABEL";
 
-// The button indexes in the back and forward segment control.
-const int kBackSegmentIndex = 0;
-const int kForwardSegmentIndex = 1;
+// This is a combined back and forward control which can no longer be selected
+// but may be in an existing customized Touch Bar. It now represents a group
+// containing the back and forward buttons, and adding the back or forward
+// buttons to the Touch Bar individually magically decomposes the group.
+NSString* const kBackForwardTouchId = @"BACK-FWD";
 
 // Touch bar icon colors values.
 const SkColor kTouchBarDefaultIconColor = SK_ColorWHITE;
@@ -95,7 +100,7 @@ NSButton* CreateTouchBarButton(const gfx::VectorIcon& icon,
                          target:owner
                          action:@selector(executeCommand:)];
   button.tag = command;
-  [button setAccessibilityLabel:l10n_util::GetNSString(tooltip_id)];
+  button.accessibilityTitle = l10n_util::GetNSString(tooltip_id);
   return button;
 }
 
@@ -128,6 +133,8 @@ ui::TouchBarAction TouchBarActionFromCommand(int command) {
 class API_AVAILABLE(macos(10.12.2)) TouchBarNotificationBridge
     : public CommandObserver,
       public BookmarkTabHelperObserver,
+      public TabStripModelObserver,
+      public content::NotificationObserver,
       public content::WebContentsObserver {
  public:
   TouchBarNotificationBridge(BrowserWindowDefaultTouchBar* owner,
@@ -135,48 +142,93 @@ class API_AVAILABLE(macos(10.12.2)) TouchBarNotificationBridge
       : owner_(owner), browser_(browser), contents_(nullptr) {
     TabStripModel* model = browser_->tab_strip_model();
     DCHECK(model);
-
+    model->AddObserver(this);
     UpdateWebContents(model->GetActiveWebContents());
+
+    auto* command_controller = browser->command_controller();
+    command_controller->AddCommandObserver(IDC_BACK, this);
+    owner.canGoBack = command_controller->IsCommandEnabled(IDC_BACK);
+    command_controller->AddCommandObserver(IDC_FORWARD, this);
+    owner.canGoBack = command_controller->IsCommandEnabled(IDC_FORWARD);
+
+    auto* profile = browser->profile();
+    auto* prefs = profile->GetPrefs();
+    show_home_button_.Init(
+        prefs::kShowHomeButton, prefs,
+        base::BindRepeating(&TouchBarNotificationBridge::UpdateTouchBar,
+                            base::Unretained(this)));
+
+    profile_pref_registrar_.Init(prefs);
+    profile_pref_registrar_.Add(
+        DefaultSearchManager::kDefaultSearchProviderDataPrefName,
+        base::BindRepeating(&TouchBarNotificationBridge::UpdateTouchBar,
+                            base::Unretained(this)));
+
+    notification_registrar_.Add(this, chrome::NOTIFICATION_PROFILE_DESTROYED,
+                                content::Source<Profile>(profile));
   }
 
+  bool show_home_button() { return show_home_button_.GetValue(); }
+
   ~TouchBarNotificationBridge() override {
-    if (contents_)
-      BookmarkTabHelper::FromWebContents(contents_)->RemoveObserver(this);
+    browser_->tab_strip_model()->RemoveObserver(this);
+    UpdateWebContents(nullptr);
   }
 
   void UpdateTouchBar() { [[owner_ controller] invalidateTouchBar]; }
 
   void UpdateWebContents(content::WebContents* new_contents) {
-    if (contents_) {
+    if (contents_ == new_contents)
+      return;
+    if (contents_)
       BookmarkTabHelper::FromWebContents(contents_)->RemoveObserver(this);
-    }
 
     contents_ = new_contents;
-    Observe(contents_);
 
-    bool is_starred = false;
-    if (contents_) {
-      BookmarkTabHelper* helper = BookmarkTabHelper::FromWebContents(contents_);
-      helper->AddObserver(this);
-      is_starred = helper->is_starred();
-    }
+    // Stop observing the old WebContents and start observing the new one (if
+    // nonnull). Qualified to disambiguate from NotificationObserver::Observe().
+    WebContentsObserver::Observe(contents_);
+
+    BookmarkTabHelper* bookmark_helper =
+        contents_ ? BookmarkTabHelper::FromWebContents(contents_) : nullptr;
+    if (bookmark_helper)
+      bookmark_helper->AddObserver(this);
 
-    [owner_ setIsPageLoading:contents_ && contents_->IsLoading()];
-    [owner_ setIsStarred:is_starred];
+    owner_.isPageLoading = contents_ && contents_->IsLoading();
+    owner_.isStarred = bookmark_helper && bookmark_helper->is_starred();
+    UpdateTouchBar();
   }
 
   // BookmarkTabHelperObserver:
   void URLStarredChanged(content::WebContents* web_contents,
                          bool starred) override {
     DCHECK(web_contents == contents_);
-    [owner_ setIsStarred:starred];
+    owner_.isStarred = starred;
   }
 
  protected:
   // CommandObserver:
   void EnabledStateChangedForCommand(int command, bool enabled) override {
     DCHECK(command == IDC_BACK || command == IDC_FORWARD);
-    [owner_ updateBackForwardControl];
+    if (command == IDC_BACK)
+      owner_.canGoBack = enabled;
+    else if (command == IDC_FORWARD)
+      owner_.canGoForward = enabled;
+  }
+
+  // TabStripModelObserver:
+  void OnTabStripModelChanged(
+      TabStripModel* tab_strip_model,
+      const TabStripModelChange& change,
+      const TabStripSelectionChange& selection) override {
+    UpdateWebContents(selection.new_contents);
+  }
+
+  // NotificationObserver:
+  void Observe(int type,
+               const content::NotificationSource& source,
+               const content::NotificationDetails& details) override {
+    owner_.browser = nullptr;
   }
 
   // WebContentsObserver:
@@ -187,52 +239,40 @@ class API_AVAILABLE(macos(10.12.2)) TouchBarNotificationBridge
 
   void DidStartLoading() override {
     DCHECK(contents_ && contents_->IsLoading());
-    [owner_ setIsPageLoading:YES];
+    owner_.isPageLoading = YES;
   }
 
   void DidStopLoading() override {
     DCHECK(contents_ && !contents_->IsLoading());
-    [owner_ setIsPageLoading:NO];
+    owner_.isPageLoading = NO;
   }
 
+  void WebContentsDestroyed() override { UpdateWebContents(nullptr); }
+
  private:
   BrowserWindowDefaultTouchBar* owner_;  // Weak.
   Browser* browser_;                     // Weak.
   content::WebContents* contents_;       // Weak.
 
+  // Used to monitor the optional home button pref.
+  BooleanPrefMember show_home_button_;
+
+  content::NotificationRegistrar notification_registrar_;
+
+  PrefChangeRegistrar profile_pref_registrar_;
+
   DISALLOW_COPY_AND_ASSIGN(TouchBarNotificationBridge);
 };
 
-id<NSAccessibility> ToNSAccessibility(id object) {
-  return [object conformsToProtocol:@protocol(NSAccessibility)] ? object : nil;
-}
-
 }  // namespace
 
 @interface BrowserWindowDefaultTouchBar () {
-  // Used to execute commands such as navigating back and forward.
-  CommandUpdater* commandUpdater_;  // Weak, owned by Browser.
-
-  // The browser associated with the touch bar.
-  Browser* browser_;  // Weak.
-
-  BrowserWindowTouchBarController* controller_;  // Weak.
-
-  // Used to monitor the optional home button pref.
-  BooleanPrefMember showHomeButton_;
-
-  // Used to listen for default search engine pref changes.
-  PrefChangeRegistrar profilePrefRegistrar_;
-
   // Used to receive and handle notifications.
   std::unique_ptr<TouchBarNotificationBridge> notificationBridge_;
 
   // The stop/reload button in the touch bar.
   base::scoped_nsobject<NSButton> reloadStopButton_;
 
-  // The back/forward segmented control in the touch bar.
-  base::scoped_nsobject<NSSegmentedControl> backForwardControl_;
-
   // The starred button in the touch bar.
   base::scoped_nsobject<NSButton> starredButton_;
 }
@@ -240,9 +280,6 @@ id<NSAccessibility> ToNSAccessibility(id object) {
 // Creates and returns a touch bar for tab fullscreen mode.
 - (NSTouchBar*)createTabFullscreenTouchBar;
 
-// Sets up the back and forward segmented control.
-- (void)setupBackForwardControl;
-
 // Updates the starred button in the touch bar.
 - (void)updateStarredButton;
 
@@ -255,35 +292,10 @@ id<NSAccessibility> ToNSAccessibility(id object) {
 
 @synthesize isPageLoading = isPageLoading_;
 @synthesize isStarred = isStarred_;
-
-- (instancetype)initWithBrowser:(Browser*)browser
-                     controller:(BrowserWindowTouchBarController*)controller {
-  if ((self = [super init])) {
-    DCHECK(browser);
-    browser_ = browser;
-    controller_ = controller;
-
-    notificationBridge_.reset(new TouchBarNotificationBridge(self, browser));
-
-    commandUpdater_ = browser->command_controller();
-    commandUpdater_->AddCommandObserver(IDC_BACK, notificationBridge_.get());
-    commandUpdater_->AddCommandObserver(IDC_FORWARD, notificationBridge_.get());
-
-    PrefService* prefs = browser->profile()->GetPrefs();
-    showHomeButton_.Init(
-        prefs::kShowHomeButton, prefs,
-        base::BindRepeating(&TouchBarNotificationBridge::UpdateTouchBar,
-                            base::Unretained(notificationBridge_.get())));
-
-    profilePrefRegistrar_.Init(prefs);
-    profilePrefRegistrar_.Add(
-        DefaultSearchManager::kDefaultSearchProviderDataPrefName,
-        base::BindRepeating(&TouchBarNotificationBridge::UpdateTouchBar,
-                            base::Unretained(notificationBridge_.get())));
-  }
-
-  return self;
-}
+@synthesize canGoBack = canGoBack_;
+@synthesize canGoForward = canGoForward_;
+@synthesize controller = controller_;
+@synthesize browser = browser_;
 
 - (NSTouchBar*)makeTouchBar {
   // When in tab or extension fullscreen, we should show a touch bar containing
@@ -301,12 +313,12 @@ id<NSAccessibility> ToNSAccessibility(id object) {
       setCustomizationIdentifier:ui::GetTouchBarId(kBrowserWindowTouchBarId)];
   [touchBar setDelegate:self];
 
-  NSMutableArray* customIdentifiers = [NSMutableArray arrayWithCapacity:7];
-  NSMutableArray* defaultIdentifiers = [NSMutableArray arrayWithCapacity:6];
+  NSMutableArray<NSString*>* customIdentifiers = [NSMutableArray array];
+  NSMutableArray<NSString*>* defaultIdentifiers = [NSMutableArray array];
 
-  NSArray* touchBarItems = @[
-    kBackForwardTouchId, kReloadOrStopTouchId, kHomeTouchId, kSearchTouchId,
-    kStarTouchId, kNewTabTouchId
+  NSArray<NSString*>* touchBarItems = @[
+    kBackTouchId, kForwardTouchId, kReloadOrStopTouchId, kHomeTouchId,
+    kSearchTouchId, kStarTouchId, kNewTabTouchId
   ];
 
   for (NSString* item in touchBarItems) {
@@ -315,8 +327,10 @@ id<NSAccessibility> ToNSAccessibility(id object) {
     [customIdentifiers addObject:itemIdentifier];
 
     // Don't add the home button if it's not shown in the toolbar.
-    if (showHomeButton_.GetValue() || ![item isEqualTo:kHomeTouchId])
-      [defaultIdentifiers addObject:itemIdentifier];
+    if (item == kHomeTouchId && !notificationBridge_->show_home_button())
+      continue;
+
+    [defaultIdentifiers addObject:itemIdentifier];
   }
 
   [customIdentifiers addObject:NSTouchBarItemIdentifierFlexibleSpace];
@@ -332,14 +346,41 @@ id<NSAccessibility> ToNSAccessibility(id object) {
   if (!touchBar)
     return nil;
 
+  if ([identifier hasSuffix:kBackForwardTouchId]) {
+    auto* items = @[
+      [touchBar itemForIdentifier:ui::GetTouchBarItemId(
+                                      kBrowserWindowTouchBarId, kBackTouchId)],
+      [touchBar
+          itemForIdentifier:ui::GetTouchBarItemId(kBrowserWindowTouchBarId,
+                                                  kForwardTouchId)],
+    ];
+    auto groupItem = [NSGroupTouchBarItem groupItemWithIdentifier:identifier
+                                                            items:items];
+    [groupItem setCustomizationLabel:
+                   l10n_util::GetNSString(
+                       IDS_TOUCH_BAR_BACK_FORWARD_CUSTOMIZATION_LABEL)];
+    return groupItem;
+  }
+
   base::scoped_nsobject<NSCustomTouchBarItem> touchBarItem(
       [[ui::NSCustomTouchBarItem() alloc] initWithIdentifier:identifier]);
-  if ([identifier hasSuffix:kBackForwardTouchId]) {
-    [self updateBackForwardControl];
-    [touchBarItem setView:backForwardControl_.get()];
-    [touchBarItem setCustomizationLabel:
-                      l10n_util::GetNSString(
-                          IDS_TOUCH_BAR_BACK_FORWARD_CUSTOMIZATION_LABEL)];
+  if ([identifier hasSuffix:kBackTouchId]) {
+    auto* button = CreateTouchBarButton(vector_icons::kBackArrowIcon, self,
+                                        IDC_BACK, IDS_ACCNAME_BACK);
+    [button bind:@"enabled" toObject:self withKeyPath:@"canGoBack" options:nil];
+    [touchBarItem setView:button];
+    [touchBarItem
+        setCustomizationLabel:l10n_util::GetNSString(IDS_ACCNAME_BACK)];
+  } else if ([identifier hasSuffix:kForwardTouchId]) {
+    auto* button = CreateTouchBarButton(vector_icons::kForwardArrowIcon, self,
+                                        IDC_FORWARD, IDS_ACCNAME_FORWARD);
+    [button bind:@"enabled"
+           toObject:self
+        withKeyPath:@"canGoForward"
+            options:nil];
+    [touchBarItem setView:button];
+    [touchBarItem
+        setCustomizationLabel:l10n_util::GetNSString(IDS_ACCNAME_FORWARD)];
   } else if ([identifier hasSuffix:kReloadOrStopTouchId]) {
     [self updateReloadStopButton];
     [touchBarItem setView:reloadStopButton_.get()];
@@ -398,6 +439,8 @@ id<NSAccessibility> ToNSAccessibility(id object) {
 
     [touchBarItem
         setView:[NSTextField labelWithAttributedString:attributedString.get()]];
+  } else {
+    return nil;
   }
 
   return touchBarItem.autorelease();
@@ -412,61 +455,12 @@ id<NSAccessibility> ToNSAccessibility(id object) {
   return touchBar.autorelease();
 }
 
-- (void)setupBackForwardControl {
-  NSMutableArray* images = [NSMutableArray arrayWithArray:@[
-    CreateNSImageFromIcon(vector_icons::kBackArrowIcon),
-    CreateNSImageFromIcon(vector_icons::kForwardArrowIcon)
-  ]];
-
-  // Offset the icons so that it matches the height of the other Touch Bar
-  // items.
-  const int kIconYOffset = 2;
-  for (NSUInteger i = 0; i < [images count]; i++) {
-    NSImage* image = [images objectAtIndex:i];
-    NSSize size = [image size];
-    size.height += kIconYOffset;
-
-    NSImage* offsettedImage = [[[NSImage alloc] initWithSize:size] autorelease];
-    [offsettedImage lockFocus];
-    [image drawInRect:NSMakeRect(0, 0, size.width, size.height - kIconYOffset)];
-    [offsettedImage unlockFocus];
-    [images replaceObjectAtIndex:i withObject:offsettedImage];
-  }
-
-  NSSegmentedControl* control = [NSSegmentedControl
-      segmentedControlWithImages:images
-                    trackingMode:NSSegmentSwitchTrackingMomentary
-                          target:self
-                          action:@selector(backOrForward:)];
-
-  // Use the accessibility protocol to get the children.
-  // Use NSAccessibilityUnignoredDescendant to be sure we start with
-  // the correct object.
-  id<NSAccessibility> segmentElement =
-      ToNSAccessibility(NSAccessibilityUnignoredDescendant(control));
-  DCHECK(segmentElement);
-  NSArray<id<NSAccessibility>>* segments = segmentElement.accessibilityChildren;
-  ToNSAccessibility(segments[0]).accessibilityTitle =
-      l10n_util::GetNSString(IDS_ACCNAME_BACK);
-  ToNSAccessibility(segments[1]).accessibilityTitle =
-      l10n_util::GetNSString(IDS_ACCNAME_FORWARD);
-
-  backForwardControl_.reset([control retain]);
-}
-
-- (void)updateWebContents:(content::WebContents*)contents {
-  notificationBridge_->UpdateWebContents(contents);
-}
-
-- (void)updateBackForwardControl {
-  if (!backForwardControl_)
-    [self setupBackForwardControl];
-
-  [backForwardControl_ setSegmentStyle:NSSegmentStyleSeparated];
-  [backForwardControl_ setEnabled:commandUpdater_->IsCommandEnabled(IDC_BACK)
-                       forSegment:kBackSegmentIndex];
-  [backForwardControl_ setEnabled:commandUpdater_->IsCommandEnabled(IDC_FORWARD)
-                       forSegment:kForwardSegmentIndex];
+- (void)setBrowser:(Browser*)browser {
+  if (browser_ == browser)
+    return;
+  browser_ = browser;
+  notificationBridge_.reset(
+      browser_ ? new TouchBarNotificationBridge(self, browser_) : nullptr);
 }
 
 - (void)updateStarredButton {
@@ -485,10 +479,6 @@ id<NSAccessibility> ToNSAccessibility(id object) {
   [starredButton_ setAccessibilityLabel:l10n_util::GetNSString(tooltipId)];
 }
 
-- (BrowserWindowTouchBarController*)controller {
-  return controller_;
-}
-
 - (NSView*)searchTouchBarView {
   TemplateURLService* templateUrlService =
       TemplateURLServiceFactory::GetForProfile(browser_->profile());
@@ -532,18 +522,10 @@ id<NSAccessibility> ToNSAccessibility(id object) {
   return searchButton;
 }
 
-- (void)backOrForward:(id)sender {
-  NSSegmentedControl* control = sender;
-  int command =
-      [control selectedSegment] == kBackSegmentIndex ? IDC_BACK : IDC_FORWARD;
-  LogTouchBarUMA(TouchBarActionFromCommand(command));
-  commandUpdater_->ExecuteCommand(command);
-}
-
 - (void)executeCommand:(id)sender {
   int command = [sender tag];
   ui::LogTouchBarUMA(TouchBarActionFromCommand(command));
-  commandUpdater_->ExecuteCommand(command);
+  browser_->command_controller()->ExecuteCommand(command);
 }
 
 - (void)setIsPageLoading:(BOOL)isPageLoading {
@@ -561,6 +543,23 @@ id<NSAccessibility> ToNSAccessibility(id object) {
 // Private methods exposed for testing.
 @implementation BrowserWindowDefaultTouchBar (ExposedForTesting)
 
++ (NSString*)reloadOrStopItemIdentifier {
+  return ui::GetTouchBarItemId(kBrowserWindowTouchBarId, kReloadOrStopTouchId);
+}
+
++ (NSString*)backItemIdentifier {
+  return ui::GetTouchBarItemId(kBrowserWindowTouchBarId, kBackTouchId);
+}
+
++ (NSString*)forwardItemIdentifier {
+  return ui::GetTouchBarItemId(kBrowserWindowTouchBarId, kForwardTouchId);
+}
+
++ (NSString*)fullscreenOriginItemIdentifier {
+  return ui::GetTouchBarItemId(kTabFullscreenTouchBarId,
+                               kFullscreenOriginLabelTouchId);
+}
+
 - (void)updateReloadStopButton {
   const gfx::VectorIcon& icon =
       isPageLoading_ ? kNavigateStopIcon : vector_icons::kReloadIcon;
@@ -586,13 +585,6 @@ id<NSAccessibility> ToNSAccessibility(id object) {
   return reloadStopButton_.get();
 }
 
-- (NSSegmentedControl*)backForwardControl {
-  if (!backForwardControl_)
-    [self updateBackForwardControl];
-
-  return backForwardControl_.get();
-}
-
 - (BookmarkTabHelperObserver*)bookmarkTabObserver {
   return notificationBridge_.get();
 }

chrome/browser/ui/cocoa/touchbar/browser_window_default_touch_bar_unittest.mm

@@ -18,33 +18,14 @@
 #include "chrome/common/pref_names.h"
 #include "components/prefs/pref_service.h"
 #include "components/strings/grit/components_strings.h"
+#include "content/public/test/test_renderer_host.h"
+#include "content/public/test/web_contents_tester.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/gtest_mac.h"
 #import "third_party/ocmock/OCMock/OCMock.h"
 #import "ui/base/cocoa/touch_bar_util.h"
 #include "ui/base/l10n/l10n_util_mac.h"
 
-namespace {
-
-// Touch bar identifiers.
-NSString* const kBrowserWindowTouchBarId = @"browser-window";
-NSString* const kTabFullscreenTouchBarId = @"tab-fullscreen";
-
-// Touch bar items identifiers.
-NSString* const kBackForwardTouchId = @"BACK-FWD";
-NSString* const kReloadOrStopTouchId = @"RELOAD-STOP";
-NSString* const kHomeTouchId = @"HOME";
-NSString* const kSearchTouchId = @"SEARCH";
-NSString* const kStarTouchId = @"BOOKMARK";
-NSString* const kNewTabTouchId = @"NEW-TAB";
-NSString* const kFullscreenOriginLabelTouchId = @"FULLSCREEN-ORIGIN-LABEL";
-
-// The button indexes in the back and forward segment control.
-const int kBackSegmentIndex = 0;
-const int kForwardSegmentIndex = 1;
-
-}  // namespace
-
 class BrowserWindowDefaultTouchBarUnitTest : public CocoaProfileTest {
  public:
   void SetUp() override {
@@ -53,75 +34,117 @@ class BrowserWindowDefaultTouchBarUnitTest : public CocoaProfileTest {
 
     command_updater_ = browser()->command_controller();
 
+    browser()->tab_strip_model()->AppendWebContents(
+        content::WebContentsTester::CreateTestWebContents(profile(), nullptr),
+        true);
+
     if (@available(macOS 10.12.2, *)) {
-      touch_bar_.reset([[BrowserWindowDefaultTouchBar alloc]
-          initWithBrowser:browser()
-               controller:nil]);
+      touch_bar_.reset([[BrowserWindowDefaultTouchBar alloc] init]);
+      touch_bar_.get().browser = browser();
     }
   }
 
-  NSString* GetFullscreenTouchBarItemId(NSString* id) {
-    return ui::GetTouchBarItemId(kTabFullscreenTouchBarId, id);
-  }
-
-  NSString* GetBrowserTouchBarItemId(NSString* id) {
-    return ui::GetTouchBarItemId(kBrowserWindowTouchBarId, id);
-  }
-
   void UpdateCommandEnabled(int id, bool enabled) {
     command_updater_->UpdateCommandEnabled(id, enabled);
   }
 
   void TearDown() override {
-    if (@available(macOS 10.12.2, *))
+    if (@available(macOS 10.12.2, *)) {
+      touch_bar_.get().browser = nullptr;
       touch_bar_.reset();
+    }
     CocoaProfileTest::TearDown();
   }
 
   CommandUpdater* command_updater_;  // Weak, owned by Browser.
+  content::RenderViewHostTestEnabler rvh_test_enabler_;
 
   API_AVAILABLE(macos(10.12.2))
   base::scoped_nsobject<BrowserWindowDefaultTouchBar> touch_bar_;
 };
 
-// Tests to check if the touch bar contains the correct items.
+// Test if any known identifiers no longer work. See the message in the test;
+// these identifiers may be written out to disk on users' computers if they
+// customize the Touch Bar, and the corresponding items will disappear if they
+// can no longer be created.
+TEST_F(BrowserWindowDefaultTouchBarUnitTest, HistoricTouchBarItems) {
+  if (@available(macOS 10.12.2, *)) {
+    NSTouchBar* touch_bar = [touch_bar_ makeTouchBar];
+    for (NSString* item_identifier : {
+             @"BACK-FWD",
+             @"BACK",
+             @"FORWARD",
+             @"RELOAD-STOP",
+             @"HOME",
+             @"SEARCH",
+             @"BOOKMARK",
+             @"NEW-TAB",
+         }) {
+      auto identifier =
+          ui::GetTouchBarItemId(@"browser-window", item_identifier);
+      EXPECT_NE(nil, [touch_bar itemForIdentifier:identifier])
+          << "BrowserWindowDefaultTouchBar didn't return a Touch Bar item for "
+             "an identifier that was once available ("
+          << identifier.UTF8String
+          << "). If a user's customized Touch Bar includes this item, it will "
+             "disappear! Do not update or remove entries in this list just to "
+             "make the test pass; keep supporting old identifiers when "
+             "possible, even if they're no longer part of the set of "
+             "default/customizable items.";
+    }
+  }
+}
+
+// Tests if BrowserWindowDefaultTouchBar can produce the items it says it can
+// and, for each kind of bar, also verify that the advertised/customizable lists
+// include some representative items (if not, the lists might be wrong.)
 TEST_F(BrowserWindowDefaultTouchBarUnitTest, TouchBarItems) {
   if (@available(macOS 10.12.2, *)) {
+    auto test_default_identifiers =
+        [&](NSSet* expected_identifiers) API_AVAILABLE(macos(10.12.2)) {
+          NSTouchBar* touch_bar = [touch_bar_ makeTouchBar];
+          NSMutableSet<NSString*>* advertised_identifiers = [NSMutableSet set];
+          [advertised_identifiers
+              addObjectsFromArray:touch_bar.defaultItemIdentifiers];
+          [advertised_identifiers
+              addObjectsFromArray:touch_bar
+                                      .customizationAllowedItemIdentifiers];
+          [advertised_identifiers
+              addObjectsFromArray:touch_bar
+                                      .customizationRequiredItemIdentifiers];
+          EXPECT_TRUE(
+              [expected_identifiers isSubsetOfSet:advertised_identifiers])
+              << "Didn't find the expected identifiers "
+              << expected_identifiers.description.UTF8String
+              << " in the set of advertised identifiers "
+              << advertised_identifiers.description.UTF8String << ".";
+          for (NSString* identifier in advertised_identifiers) {
+            EXPECT_NE(nil, [touch_bar itemForIdentifier:identifier])
+                << "Didn't get a touch bar item for " << identifier.UTF8String;
+          }
+        };
+
     // Set to tab fullscreen.
     FullscreenController* fullscreen_controller =
         browser()->exclusive_access_manager()->fullscreen_controller();
     fullscreen_controller->set_is_tab_fullscreen_for_testing(true);
     EXPECT_TRUE(fullscreen_controller->IsTabFullscreen());
 
-    // The touch bar should only contain an item that displays the origin of the
-    // tab content fullscreen.
-    NSTouchBar* touch_bar = [touch_bar_ makeTouchBar];
-    NSArray* touch_bar_items = [touch_bar itemIdentifiers];
-    EXPECT_TRUE(
-        [touch_bar_items containsObject:GetFullscreenTouchBarItemId(
-                                            kFullscreenOriginLabelTouchId)]);
-    EXPECT_EQ(1u, [touch_bar_items count]);
+    // The fullscreen Touch Bar should include *at least* these items.
+    test_default_identifiers([NSSet setWithArray:@[
+      BrowserWindowDefaultTouchBar.fullscreenOriginItemIdentifier,
+    ]]);
 
     // Exit fullscreen.
     fullscreen_controller->set_is_tab_fullscreen_for_testing(false);
     EXPECT_FALSE(fullscreen_controller->IsTabFullscreen());
 
-    PrefService* prefs = profile()->GetPrefs();
-    DCHECK(prefs);
-    prefs->SetBoolean(prefs::kShowHomeButton, true);
-    touch_bar_items = [[touch_bar_ makeTouchBar] itemIdentifiers];
-    EXPECT_TRUE([touch_bar_items
-        containsObject:GetBrowserTouchBarItemId(kBackForwardTouchId)]);
-    EXPECT_TRUE([touch_bar_items
-        containsObject:GetBrowserTouchBarItemId(kReloadOrStopTouchId)]);
-    EXPECT_TRUE([touch_bar_items
-        containsObject:GetBrowserTouchBarItemId(kHomeTouchId)]);
-    EXPECT_TRUE([touch_bar_items
-        containsObject:GetBrowserTouchBarItemId(kSearchTouchId)]);
-    EXPECT_TRUE([touch_bar_items
-        containsObject:GetBrowserTouchBarItemId(kStarTouchId)]);
-    EXPECT_TRUE([touch_bar_items
-        containsObject:GetBrowserTouchBarItemId(kNewTabTouchId)]);
+    // The default Touch Bar should include *at least* these items.
+    test_default_identifiers([NSSet setWithArray:@[
+      BrowserWindowDefaultTouchBar.backItemIdentifier,
+      BrowserWindowDefaultTouchBar.forwardItemIdentifier,
+      BrowserWindowDefaultTouchBar.reloadOrStopItemIdentifier,
+    ]]);
   }
 }
 
@@ -131,56 +154,69 @@ TEST_F(BrowserWindowDefaultTouchBarUnitTest, ReloadOrStopTouchBarItem) {
     NSTouchBar* touch_bar = [touch_bar_ makeTouchBar];
     [touch_bar_ setIsPageLoading:NO];
 
-    NSTouchBarItem* item = [touch_bar_
-                     touchBar:touch_bar
-        makeItemForIdentifier:GetBrowserTouchBarItemId(kReloadOrStopTouchId)];
+    NSTouchBarItem* item =
+        [touch_bar itemForIdentifier:BrowserWindowDefaultTouchBar
+                                         .reloadOrStopItemIdentifier];
     EXPECT_EQ(IDC_RELOAD, [[item view] tag]);
 
     [touch_bar_ setIsPageLoading:YES];
-    item = [touch_bar_ touchBar:touch_bar
-          makeItemForIdentifier:GetBrowserTouchBarItemId(kReloadOrStopTouchId)];
+    item = [touch_bar itemForIdentifier:BrowserWindowDefaultTouchBar
+                                            .reloadOrStopItemIdentifier];
     EXPECT_EQ(IDC_STOP, [[item view] tag]);
   }
 }
 
-// Tests to see if the back/forward items on the touch bar is in sync with the
-// back and forward commands.
-TEST_F(BrowserWindowDefaultTouchBarUnitTest, BackForwardCommandUpdate) {
+// Tests if the back button on the touch bar is in sync with the back command.
+TEST_F(BrowserWindowDefaultTouchBarUnitTest, BackCommandUpdate) {
   if (@available(macOS 10.12.2, *)) {
-    NSSegmentedControl* back_forward_control = [touch_bar_ backForwardControl];
+    NSTouchBar* touch_bar = [touch_bar_ makeTouchBar];
+    NSTouchBarItem* item = [touch_bar
+        itemForIdentifier:BrowserWindowDefaultTouchBar.backItemIdentifier];
+    NSButton* button = base::mac::ObjCCast<NSButton>(item.view);
 
     UpdateCommandEnabled(IDC_BACK, true);
-    UpdateCommandEnabled(IDC_FORWARD, true);
-    EXPECT_TRUE([back_forward_control isEnabledForSegment:kBackSegmentIndex]);
-    EXPECT_TRUE(
-        [back_forward_control isEnabledForSegment:kForwardSegmentIndex]);
-
+    EXPECT_TRUE(button.enabled);
     UpdateCommandEnabled(IDC_BACK, false);
-    EXPECT_FALSE([back_forward_control isEnabledForSegment:kBackSegmentIndex]);
-    EXPECT_TRUE(
-        [back_forward_control isEnabledForSegment:kForwardSegmentIndex]);
+    EXPECT_FALSE(button.enabled);
+  }
+}
 
+// Tests if the forward button on the touch bar is in sync with the forward
+// command.
+TEST_F(BrowserWindowDefaultTouchBarUnitTest, ForwardCommandUpdate) {
+  if (@available(macOS 10.12.2, *)) {
+    NSTouchBar* touch_bar = [touch_bar_ makeTouchBar];
+    NSTouchBarItem* item = [touch_bar
+        itemForIdentifier:BrowserWindowDefaultTouchBar.forwardItemIdentifier];
+    NSButton* button = base::mac::ObjCCast<NSButton>(item.view);
+
+    UpdateCommandEnabled(IDC_FORWARD, true);
+    EXPECT_TRUE(button.enabled);
     UpdateCommandEnabled(IDC_FORWARD, false);
-    EXPECT_FALSE([back_forward_control isEnabledForSegment:kBackSegmentIndex]);
-    EXPECT_FALSE(
-        [back_forward_control isEnabledForSegment:kForwardSegmentIndex]);
+    EXPECT_FALSE(button.enabled);
   }
 }
 
-TEST_F(BrowserWindowDefaultTouchBarUnitTest, BackForwardAccessibilityLabels) {
+TEST_F(BrowserWindowDefaultTouchBarUnitTest, BackAccessibilityLabel) {
   if (@available(macOS 10.12.2, *)) {
-    NSSegmentedControl* control = touch_bar_.get().backForwardControl;
-    id<NSAccessibility> cell = NSAccessibilityUnignoredDescendant(control);
-    ASSERT_TRUE([cell conformsToProtocol:@protocol(NSAccessibility)]);
-
-    id<NSAccessibility> back = cell.accessibilityChildren[0];
-    EXPECT_TRUE([back conformsToProtocol:@protocol(NSAccessibility)]);
-    EXPECT_NSEQ(back.accessibilityTitle,
+    NSTouchBar* touch_bar = [touch_bar_ makeTouchBar];
+    NSTouchBarItem* item = [touch_bar
+        itemForIdentifier:BrowserWindowDefaultTouchBar.backItemIdentifier];
+    id<NSAccessibility> view = item.view;
+    ASSERT_TRUE([view conformsToProtocol:@protocol(NSAccessibility)]);
+    EXPECT_NSEQ(view.accessibilityTitle,
                 l10n_util::GetNSString(IDS_ACCNAME_BACK));
+  }
+}
 
-    id<NSAccessibility> forward = cell.accessibilityChildren[1];
-    EXPECT_TRUE([forward conformsToProtocol:@protocol(NSAccessibility)]);
-    EXPECT_NSEQ(forward.accessibilityTitle,
+TEST_F(BrowserWindowDefaultTouchBarUnitTest, ForwardAccessibilityLabel) {
+  if (@available(macOS 10.12.2, *)) {
+    NSTouchBar* touch_bar = [touch_bar_ makeTouchBar];
+    NSTouchBarItem* item = [touch_bar
+        itemForIdentifier:BrowserWindowDefaultTouchBar.forwardItemIdentifier];
+    id<NSAccessibility> view = item.view;
+    ASSERT_TRUE([view conformsToProtocol:@protocol(NSAccessibility)]);
+    EXPECT_NSEQ(view.accessibilityTitle,
                 l10n_util::GetNSString(IDS_ACCNAME_FORWARD));
   }
 }

chrome/browser/ui/cocoa/touchbar/browser_window_touch_bar_controller.h

@@ -32,9 +32,6 @@ API_AVAILABLE(macos(10.12.2))
 // nil.
 - (void)invalidateTouchBar;
 
-- (void)updateWebContents:(content::WebContents*)contents;
-
-- (content::WebContents*)webContents;
 @end
 
 @interface BrowserWindowTouchBarController (ExposedForTesting)

chrome/browser/ui/cocoa/touchbar/browser_window_touch_bar_controller.mm

@@ -19,66 +19,9 @@
 #include "content/public/browser/web_contents_observer.h"
 #import "ui/base/cocoa/touch_bar_util.h"
 
-class API_AVAILABLE(macos(10.12.2)) WebContentsNotificationBridge
-    : public TabStripModelObserver,
-      public content::WebContentsObserver {
- public:
-  WebContentsNotificationBridge(BrowserWindowTouchBarController* owner,
-                                Browser* browser)
-      : owner_(owner), browser_(browser), contents_(nullptr) {
-    TabStripModel* model = browser_->tab_strip_model();
-    DCHECK(model);
-    model->AddObserver(this);
-
-    UpdateWebContents(model->GetActiveWebContents());
-  }
-
-  ~WebContentsNotificationBridge() override {
-    TabStripModel* model = browser_->tab_strip_model();
-    if (model)
-      model->RemoveObserver(this);
-  }
-
-  void UpdateWebContents(content::WebContents* new_contents) {
-    contents_ = new_contents;
-    Observe(contents_);
-
-    [owner_ updateWebContents:contents_];
-  }
-
-  // TabStripModelObserver:
-  void OnTabStripModelChanged(
-      TabStripModel* tab_strip_model,
-      const TabStripModelChange& change,
-      const TabStripSelectionChange& selection) override {
-    if (tab_strip_model->empty() || !selection.active_tab_changed())
-      return;
-
-    UpdateWebContents(selection.new_contents);
-    contents_ = selection.new_contents;
-  }
-
-  content::WebContents* contents() const { return contents_; }
-
- protected:
-  // WebContentsObserver:
-  void WebContentsDestroyed() override {
-    // Clean up if the web contents is being destroyed.
-    UpdateWebContents(nullptr);
-  }
-
- private:
-  BrowserWindowTouchBarController* owner_;  // Weak.
-  Browser* browser_;                        // Weak.
-  content::WebContents* contents_;          // Weak.
-};
-
 @interface BrowserWindowTouchBarController () {
   NSWindow* window_;  // Weak.
 
-  // Used to receive and handle notifications.
-  std::unique_ptr<WebContentsNotificationBridge> notificationBridge_;
-
   base::scoped_nsobject<BrowserWindowDefaultTouchBar> defaultTouchBar_;
 
   base::scoped_nsobject<WebTextfieldTouchBarController> webTextfieldTouchBar_;
@@ -92,12 +35,9 @@ class API_AVAILABLE(macos(10.12.2)) WebContentsNotificationBridge
     DCHECK(browser);
     window_ = window;
 
-    notificationBridge_ =
-        std::make_unique<WebContentsNotificationBridge>(self, browser);
-
-    defaultTouchBar_.reset([[BrowserWindowDefaultTouchBar alloc]
-        initWithBrowser:browser
-             controller:self]);
+    defaultTouchBar_.reset([[BrowserWindowDefaultTouchBar alloc] init]);
+    defaultTouchBar_.get().controller = self;
+    defaultTouchBar_.get().browser = browser;
     webTextfieldTouchBar_.reset(
         [[WebTextfieldTouchBarController alloc] initWithController:self]);
   }
@@ -105,6 +45,11 @@ class API_AVAILABLE(macos(10.12.2)) WebContentsNotificationBridge
   return self;
 }
 
+- (void)dealloc {
+  defaultTouchBar_.get().browser = nullptr;
+  [super dealloc];
+}
+
 - (void)invalidateTouchBar {
   DCHECK([window_ respondsToSelector:@selector(setTouchBar:)]);
   [window_ performSelector:@selector(setTouchBar:) withObject:nil];
@@ -118,15 +63,6 @@ class API_AVAILABLE(macos(10.12.2)) WebContentsNotificationBridge
   return [defaultTouchBar_ makeTouchBar];
 }
 
-- (void)updateWebContents:(content::WebContents*)contents {
-  [defaultTouchBar_ updateWebContents:contents];
-  [self invalidateTouchBar];
-}
-
-- (content::WebContents*)webContents {
-  return notificationBridge_->web_contents();
-}
-
 @end
 
 @implementation BrowserWindowTouchBarController (ExposedForTesting)