[ios] Add experiment flag for Tab Grid

This CL adds an experiment flag for Tab Grid,
and simply uses the flag to show a blank tab
grid when enabled.

Bug: 804496
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I9d24d64c77cba8889f2c699763d610617263b9cc
Reviewed-on: https://chromium-review.googlesource.com/917427
Commit-Queue: edchin <edchin@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Reviewed-by: edchin <edchin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536751}

ios/chrome/app/BUILD.gn

@@ -200,6 +200,7 @@ source_set("app_internal") {
     "//ios/chrome/browser/ui/settings",
     "//ios/chrome/browser/ui/signin_interaction",
     "//ios/chrome/browser/ui/stack_view",
+    "//ios/chrome/browser/ui/tab_grid",
     "//ios/chrome/browser/ui/tab_switcher",
     "//ios/chrome/browser/ui/tabs",
     "//ios/chrome/browser/ui/toolbar/clean:toolbar_ui",

ios/chrome/app/main_controller.mm

@@ -133,6 +133,7 @@
 #import "ios/chrome/browser/ui/settings/settings_navigation_controller.h"
 #import "ios/chrome/browser/ui/signin_interaction/signin_interaction_coordinator.h"
 #import "ios/chrome/browser/ui/stack_view/stack_view_controller.h"
+#include "ios/chrome/browser/ui/tab_grid/tab_grid_view_controller.h"
 #import "ios/chrome/browser/ui/tab_switcher/tab_switcher_controller.h"
 #import "ios/chrome/browser/ui/toolbar/public/omnibox_focuser.h"
 #include "ios/chrome/browser/ui/ui_util.h"
@@ -1871,20 +1872,7 @@ void MainControllerAuthenticationServiceDelegate::ClearBrowsingData(
   }
 
   if (!_tabSwitcherController) {
-    if (IsIPadIdiom()) {
-      _tabSwitcherController = [[TabSwitcherController alloc]
-                initWithBrowserState:_mainBrowserState
-                        mainTabModel:self.mainTabModel
-                         otrTabModel:self.otrTabModel
-                      activeTabModel:self.currentTabModel
-          applicationCommandEndpoint:self];
-    } else {
-      _tabSwitcherController =
-          [[StackViewController alloc] initWithMainTabModel:self.mainTabModel
-                                                otrTabModel:self.otrTabModel
-                                             activeTabModel:self.currentTabModel
-                                 applicationCommandEndpoint:self];
-    }
+    _tabSwitcherController = [self newTabSwitcherController];
   } else {
     // The StackViewController is kept in memory to avoid the performance hit of
     // loading from the nib on next showing, but clears out its card models to
@@ -2522,6 +2510,29 @@ void MainControllerAuthenticationServiceDelegate::ClearBrowsingData(
   [self.mainTabModel closeAllTabs];
 }
 
+#pragma mark - Experimental flag
+
+- (UIViewController<TabSwitcher>*)newTabSwitcherController {
+  if (IsTabSwitcherTabGridEnabled()) {
+    return [[TabGridViewController alloc] init];
+  } else {
+    if (IsIPadIdiom()) {
+      return [[TabSwitcherController alloc]
+                initWithBrowserState:_mainBrowserState
+                        mainTabModel:self.mainTabModel
+                         otrTabModel:self.otrTabModel
+                      activeTabModel:self.currentTabModel
+          applicationCommandEndpoint:self];
+    } else {
+      return
+          [[StackViewController alloc] initWithMainTabModel:self.mainTabModel
+                                                otrTabModel:self.otrTabModel
+                                             activeTabModel:self.currentTabModel
+                                 applicationCommandEndpoint:self];
+    }
+  }
+}
+
 @end
 
 #pragma mark - TestingOnly

ios/chrome/browser/about_flags.mm

@@ -233,6 +233,9 @@ const flags_ui::FeatureEntry kFeatureEntries[] = {
      flag_descriptions::kMailtoHandlingWithGoogleUIName,
      flag_descriptions::kMailtoHandlingWithGoogleUIDescription,
      flags_ui::kOsIos, FEATURE_VALUE_TYPE(kMailtoHandledWithGoogleUI)},
+    {"tab-switcher-tab-grid", flag_descriptions::kTabSwitcherTabGridName,
+     flag_descriptions::kTabSwitcherTabGridDescription, flags_ui::kOsIos,
+     FEATURE_VALUE_TYPE(kTabSwitcherTabGrid)},
 };
 
 // Add all switches from experimental flags to |command_line|.

ios/chrome/browser/ios_chrome_flag_descriptions.cc

@@ -126,6 +126,11 @@ const char kTabSwitcherPresentsBVCDescription[] =
     "BVC is visible, the tab switcher will remain in the VC hierarchy "
     "underneath it.";
 
+const char kTabSwitcherTabGridName[] = "TabSwitcher Tab Grid";
+const char kTabSwitcherTabGridDescription[] =
+    "When enabled, the tab grid will be used as the tab switcher for both "
+    "phone and tablet.";
+
 const char kUIRefreshPhase1Name[] = "UI Refresh Phase 1";
 const char kUIRefreshPhase1Description[] =
     "When enabled, the first phase of the iOS UI refresh will be displayed.";

ios/chrome/browser/ios_chrome_flag_descriptions.h

@@ -113,6 +113,10 @@ extern const char kShowAutofillTypePredictionsDescription[];
 extern const char kTabSwitcherPresentsBVCName[];
 extern const char kTabSwitcherPresentsBVCDescription[];
 
+// Title and description for the flag to enable the TabGrid as the tab switcher.
+extern const char kTabSwitcherTabGridName[];
+extern const char kTabSwitcherTabGridDescription[];
+
 // Title and description for the flag to enable the phase 1 UI Refresh.
 extern const char kUIRefreshPhase1Name[];
 extern const char kUIRefreshPhase1Description[];

ios/chrome/browser/ui/tab_grid/BUILD.gn

@@ -17,5 +17,6 @@ source_set("tab_grid") {
   deps = [
     "//base",
     "//ios/chrome/browser/ui/coordinators:chrome_coordinators",
+    "//ios/chrome/browser/ui/tab_switcher",
   ]
 }

ios/chrome/browser/ui/tab_grid/tab_grid_view_controller.h

@@ -7,7 +7,9 @@
 
 #import <UIKit/UIKit.h>
 
-@interface TabGridViewController : UIViewController
+#import "ios/chrome/browser/ui/tab_switcher/tab_switcher.h"
+
+@interface TabGridViewController : UIViewController<TabSwitcher>
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_TAB_GRID_TAB_GRID_VIEW_CONTROLLER_H_

ios/chrome/browser/ui/tab_grid/tab_grid_view_controller.mm

@@ -9,4 +9,44 @@
 #endif
 
 @implementation TabGridViewController
+@synthesize delegate = _delegate;
+@synthesize animationDelegate = _animationDelegate;
+@synthesize dispatcher = _dispatcher;
+@synthesize transitionContext = _transitionContext;
+
+- (void)viewDidLoad {
+  [super viewDidLoad];
+  self.view.backgroundColor = [UIColor whiteColor];
+}
+
+#pragma mark - TabSwitcher
+
+- (void)restoreInternalStateWithMainTabModel:(TabModel*)mainModel
+                                 otrTabModel:(TabModel*)otrModel
+                              activeTabModel:(TabModel*)activeModel {
+}
+
+- (UIViewController*)viewController {
+  return self;
+}
+
+- (void)prepareForDisplayAtSize:(CGSize)size {
+}
+
+- (void)showWithSelectedTabAnimation {
+}
+
+- (Tab*)dismissWithNewTabAnimationToModel:(TabModel*)targetModel
+                                  withURL:(const GURL&)url
+                                  atIndex:(NSUInteger)position
+                               transition:(ui::PageTransition)transition {
+  return nil;
+}
+
+- (void)setOtrTabModel:(TabModel*)otrModel {
+}
+
+- (void)tabSwitcherDismissWithModel:(TabModel*)model animated:(BOOL)animated {
+}
+
 @end

ios/chrome/browser/ui/ui_feature_flags.cc

@@ -6,3 +6,6 @@
 
 const base::Feature kUIRefreshPhase1{"UIRefreshPhase1",
                                      base::FEATURE_DISABLED_BY_DEFAULT};
+
+const base::Feature kTabSwitcherTabGrid{"TabSwitcherTabGrid",
+                                        base::FEATURE_DISABLED_BY_DEFAULT};

ios/chrome/browser/ui/ui_feature_flags.h

@@ -11,4 +11,8 @@
 // used directly. Instead use ui_util::IsUIRefreshPhase1Enabled().
 extern const base::Feature kUIRefreshPhase1;
 
+// Used to enable the tab grid on phone and tablet. This flag should not be
+// used directly. Instead use ui_util::IsTabSwitcherTabGridEnabled().
+extern const base::Feature kTabSwitcherTabGrid;
+
 #endif  // IOS_CHROME_BROWSER_UI_UI_FEATURE_FLAGS_H_

ios/chrome/browser/ui/ui_util.h

@@ -39,9 +39,12 @@ CGFloat CurrentScreenWidth();
 // Returns true if the device is an iPhone X.
 bool IsIPhoneX();
 
-// Returns whether the first phase of the UI refresh will be displayed..
+// Returns whether the first phase of the UI refresh will be displayed.
 bool IsUIRefreshPhase1Enabled();
 
+// Returns whether the tab grid will be displayed as the tab switcher.
+bool IsTabSwitcherTabGridEnabled();
+
 // Returns the height of the status bar, accounting for orientation.
 CGFloat StatusBarHeight();
 

ios/chrome/browser/ui/ui_util.mm

@@ -63,6 +63,10 @@ bool IsUIRefreshPhase1Enabled() {
   return base::FeatureList::IsEnabled(kUIRefreshPhase1);
 }
 
+bool IsTabSwitcherTabGridEnabled() {
+  return base::FeatureList::IsEnabled(kTabSwitcherTabGrid);
+}
+
 CGFloat StatusBarHeight() {
   // This is a temporary solution until usage of StatusBarHeight has been
   // replaced with topLayoutGuide.