[Mac] Fix Toolbar glimpse during fullscreen transition

chrome/browser/ui/cocoa/presentation_mode_controller.h

 // Copyright (c) 2012 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_PRESENTATION_MODE_CONTROLLER_H_
 #define CHROME_BROWSER_UI_COCOA_PRESENTATION_MODE_CONTROLLER_H_
 
 #include <Carbon/Carbon.h>
 #import <Cocoa/Cocoa.h>
 
@@ skipping 127 matching lines @@
 - (void)cancelAnimationAndTimers;
 
 // In any fullscreen mode, the y offset to use for the content at the top of
 // the screen (tab strip, omnibox, bookmark bar, etc).
 // Ranges from 0 to -22.
 - (CGFloat)menubarOffset;
 
 // Returns true if the window is the main window.
 - (BOOL)isMainWindow;
 
+// Returns true if the browser is in the process of entering/exiting
+// fullscreen.
+- (BOOL)isFullscreenTransitionInProgress;
+
 @end
 
 // Private methods exposed for testing.
 @interface PresentationModeController (ExposedForTesting)
 // Adjusts the AppKit Fullscreen options of the application.
 - (void)setSystemFullscreenModeTo:(base::mac::FullScreenMode)mode;
 
 // Callback for menu bar animations.
 - (void)setMenuBarRevealProgress:(CGFloat)progress;
 
 // Updates the local state that reflects the fraction of the toolbar area that
 // is showing. This function has the side effect of changing the AppKit
 // Fullscreen option for whether the menu bar is shown.
 - (void)changeToolbarFraction:(CGFloat)fraction;
 @end
 
 // Notification posted when we're about to enter or leave fullscreen.
 extern NSString* const kWillEnterFullscreenNotification;
 extern NSString* const kWillLeaveFullscreenNotification;
 
 #endif  // CHROME_BROWSER_UI_COCOA_PRESENTATION_MODE_CONTROLLER_H_