Added popup that shows the new Back shortcut on Mac.

chrome/browser/ui/cocoa/browser/exclusive_access_controller_views.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_UI_COCOA_BROWSER_EXCLUSIVE_ACCESS_CONTROLLER_VIEWS_H_
 #define CHROME_BROWSER_UI_COCOA_BROWSER_EXCLUSIVE_ACCESS_CONTROLLER_VIEWS_H_
 
 // Note this file has a _views suffix so that it may have an optional runtime
 // dependency on toolkit-views UI.
 
 #import <CoreGraphics/CoreGraphics.h>
 
 #include <memory>
 
 #import "base/mac/scoped_nsobject.h"
 #include "base/macros.h"
 #include "chrome/browser/ui/exclusive_access/exclusive_access_context.h"
 #include "chrome/browser/ui/views/exclusive_access_bubble_views_context.h"
 #include "components/prefs/pref_change_registrar.h"
 #include "ui/base/accelerators/accelerator.h"
 
 class Browser;
 class BrowserWindow;
 @class BrowserWindowController;
 class ExclusiveAccessBubbleViews;
 @class ExclusiveAccessBubbleWindowController;
 class GURL;
+class NewBackShortcutBubble;
 
 // Component placed into a browser window controller to manage communication
-// with the exclusive access bubble, which appears for events such as entering
+// with subtle notification bubbles, which appear for events such as entering
 // fullscreen.
 class ExclusiveAccessController : public ExclusiveAccessContext,
                                   public ui::AcceleratorProvider,
                                   public ExclusiveAccessBubbleViewsContext {
  public:
   ExclusiveAccessController(BrowserWindowController* controller,
                             Browser* browser);
   ~ExclusiveAccessController() override;
 
   const GURL& url() const { return url_; }
   ExclusiveAccessBubbleType bubble_type() const { return bubble_type_; }
   ExclusiveAccessBubbleWindowController* cocoa_bubble() {
     return cocoa_bubble_;
   }
 
   // Shows the bubble once the NSWindow has received -windowDidEnterFullScreen:.
   void Show();
 
+  // Shows the new Back shortcut bubble.
+  void ShowNewBackShortcutBubble(bool forward);
+
   // Closes any open bubble.
   void Destroy();
 
   // If showing, position the bubble at the given y-coordinate.
   void Layout(CGFloat max_y);
 
   // ExclusiveAccessContext:
   Profile* GetProfile() override;
   bool IsFullscreen() const override;
   bool SupportsFullscreenWithToolbar() const override;
@@ skipping 34 matching lines @@
 
   // When going fullscreen for a tab, we need to store the URL and the
   // fullscreen type, since we can't show the bubble until
   // -windowDidEnterFullScreen: gets called.
   GURL url_;
   ExclusiveAccessBubbleType bubble_type_;
 
   std::unique_ptr<ExclusiveAccessBubbleViews> views_bubble_;
   base::scoped_nsobject<ExclusiveAccessBubbleWindowController> cocoa_bubble_;
 
+  // This class also manages the new Back shortcut bubble (which functions the
+  // same way as ExclusiveAccessBubbleViews).
+  std::unique_ptr<NewBackShortcutBubble> new_back_shortcut_bubble_;
+
   // Used to keep track of the kShowFullscreenToolbar preference.
   PrefChangeRegistrar pref_registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(ExclusiveAccessController);
 };
 
 #endif  // CHROME_BROWSER_UI_COCOA_BROWSER_EXCLUSIVE_ACCESS_CONTROLLER_VIEWS_H_