[Mac][Material Design] Improve bookmark folder menu performance.

chrome/browser/ui/cocoa/bookmarks/bookmark_button.h

 // Copyright (c) 2011 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.
 
 #import <Cocoa/Cocoa.h>
 #include <vector>
 #import "chrome/browser/ui/cocoa/draggable_button.h"
 #import "chrome/browser/ui/cocoa/themed_window.h"
 #include "ui/base/window_open_disposition.h"
 
@@ skipping 10 matching lines @@
 // Protocol for a BookmarkButton's delegate, responsible for doing
 // things on behalf of a bookmark button.
 @protocol BookmarkButtonDelegate
 
 // Returns a pasteboard item that has all bookmark information.
 - (NSPasteboardItem*)pasteboardItemForDragOfButton:(BookmarkButton*)button;
 
 // Bookmark buttons pass mouseEntered: and mouseExited: events to
 // their delegate.  This allows the delegate to decide (for example)
 // which one, if any, should perform a hover-open.
-- (void)mouseEnteredButton:(id)button event:(NSEvent*)event;
-- (void)mouseExitedButton:(id)button event:(NSEvent*)event;
+//
+// mouseEnteredButton:event: is optimized to act only if the mouse is actually
+// within the button's bounds at the time of the call (with a fast moving mouse,
+// -isMouseReallyInside might return NO). Passing nil for |event| disables this
+// optimization, useful for unit testing.
+- (void)mouseEnteredButton:(BookmarkButton*)button event:(NSEvent*)event;
+- (void)mouseExitedButton:(BookmarkButton*)button event:(NSEvent*)event;
 
 // Returns YES if a drag operation should lock the fullscreen overlay bar
 // visibility before starting.  For example, dragging a bookmark button should
 // not lock the overlay if the bookmark bar is currently showing in detached
 // mode on the NTP.
 - (BOOL)dragShouldLockBarVisibility;
 
 // Returns the top-level window for this button.
 - (NSWindow*)browserWindow;
 
@@ skipping 204 matching lines @@
 + (BookmarkButton*)draggedButton;
 
 
 @end  // @interface BookmarkButton
 
 
 @interface BookmarkButton(TestingAPI)
 - (void)beginDrag:(NSEvent*)event;
 @end