[Mac]Implement ViewID support. (third approach)

chrome/browser/cocoa/bookmark_button.mm

 // Copyright (c) 2010 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 "chrome/browser/cocoa/bookmark_button.h"
 #include "base/logging.h"
 #import "base/scoped_nsobject.h"
 #include "chrome/browser/bookmarks/bookmark_model.h"
 #import "chrome/browser/cocoa/bookmark_button_cell.h"
 #import "chrome/browser/cocoa/browser_window_controller.h"
+#import "chrome/browser/cocoa/view_id_util.h"
 
 // The opacity of the bookmark button drag image.
 static const CGFloat kDragImageOpacity = 0.7;
 
 @interface BookmarkButton(Private)
 
 // Make a drag image for the button.
 - (NSImage*)dragImage;
 
 @end  // @interface BookmarkButton(Private)
 
 
 @implementation BookmarkButton
 
 @synthesize delegate = delegate_;
 
+- (id)initWithFrame:(NSRect)frameRect {
+  // BookmarkButton's ViewID may be changed to VIEW_ID_OTHER_BOOKMARKS in
+  // BookmarkBarController, so we can't just override -viewID method to return
+  // it.
+  if ((self = [super initWithFrame:frameRect]))
+    view_id_util::SetID(self, VIEW_ID_BOOKMARK_BAR_ELEMENT);
+  return self;
+}
+
+- (void)dealloc {
+  view_id_util::UnsetID(self);
+  [super dealloc];
+}
+
 - (const BookmarkNode*)bookmarkNode {
   return [[self cell] bookmarkNode];
 }
 
 - (BOOL)isFolder {
   const BookmarkNode* node = [self bookmarkNode];
   return (node && node->is_folder());
 }
 
 - (BOOL)isEmpty {
@@ skipping 107 matching lines @@
   [image drawAtPoint:NSMakePoint(0, 0)
             fromRect:NSMakeRect(0, 0, NSWidth(bounds), NSHeight(bounds))
            operation:NSCompositeSourceOver
             fraction:kDragImageOpacity];
 
   [dragImage unlockFocus];
   return dragImage;
 }
 
 @end  // @implementation BookmarkButton(Private)