[Mac] Update the Touch Bar for Default Search Engine changes

Currently, if the user changes the default search engine in
settings, the touch bar does not update to reflect the change.

To fix this issue, the BrowserWindowTouchBar is modified so
that it observers changes to the default search engine.

Tests: browser test BrowserWindowTouchBarTest.SearchEngineChanges

Bug: 696702
Change-Id: I92861aabf9ab2e87ba6d1d32fda975d9a10bdf26
Reviewed-on: https://chromium-review.googlesource.com/792034
Commit-Queue: Sarah Chan <spqchan@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#519761}

chrome/browser/ui/cocoa/browser_window_touch_bar.mm

@@ -123,7 +123,7 @@ ui::TouchBarAction TouchBarActionFromCommand(int command) {
 }
 
 // A class registered for C++ notifications. This is used to detect changes in
-// the home button preferences and the back/forward commands.
+// the profile preferences and the back/forward commands.
 class BrowserTouchBarNotificationBridge : public CommandObserver {
  public:
   BrowserTouchBarNotificationBridge(BrowserWindowTouchBar* observer,
@@ -162,6 +162,9 @@ class BrowserTouchBarNotificationBridge : public CommandObserver {
   // 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<BrowserTouchBarNotificationBridge> notificationBridge_;
 
@@ -212,6 +215,12 @@ class BrowserTouchBarNotificationBridge : public CommandObserver {
         prefs::kShowHomeButton, prefs,
         base::Bind(&BrowserTouchBarNotificationBridge::UpdateTouchBar,
                    base::Unretained(notificationBridge_.get())));
+
+    profilePrefRegistrar_.Init(prefs);
+    profilePrefRegistrar_.Add(
+        DefaultSearchManager::kDefaultSearchProviderDataPrefName,
+        base::Bind(&BrowserTouchBarNotificationBridge::UpdateTouchBar,
+                   base::Unretained(notificationBridge_.get())));
   }
 
   return self;

chrome/browser/ui/cocoa/browser_window_touch_bar_browsertest.mm

@@ -7,7 +7,10 @@
 #include "chrome/browser/ui/browser_window.h"
 #import "chrome/browser/ui/cocoa/browser_window_controller.h"
 #import "chrome/browser/ui/cocoa/browser_window_touch_bar.h"
+#include "chrome/common/pref_names.h"
 #include "chrome/test/base/in_process_browser_test.h"
+#include "components/prefs/pref_service.h"
+#include "components/search_engines/search_engines_test_util.cc"
 #include "content/public/test/browser_test_utils.h"
 #include "content/public/test/test_utils.h"
 #include "testing/gtest_mac.h"
@@ -105,3 +108,26 @@ IN_PROC_BROWSER_TEST_F(BrowserWindowTouchBarTest, StarredChanges) {
     EXPECT_NE(touch_bar, [window touchBar]);
   }
 }
+
+// Tests if the touch bar gets invalidated if the default search engine has
+// changed.
+IN_PROC_BROWSER_TEST_F(BrowserWindowTouchBarTest, SearchEngineChanges) {
+  if (@available(macOS 10.12.2, *)) {
+    PrefService* prefs = browser()->profile()->GetPrefs();
+    DCHECK(prefs);
+
+    NSWindow* window = [browser_window_controller() window];
+    NSTouchBar* touch_bar = [browser_touch_bar() makeTouchBar];
+    [window setTouchBar:touch_bar];
+    EXPECT_TRUE([window touchBar]);
+
+    // Change the default search engine.
+    std::unique_ptr<TemplateURLData> data =
+        GenerateDummyTemplateURLData("poutine");
+    prefs->Set(DefaultSearchManager::kDefaultSearchProviderDataPrefName,
+               *TemplateURLDataToDictionary(*data));
+
+    // The window should have a new touch bar.
+    EXPECT_NE(touch_bar, [window touchBar]);
+  }
+}