[Mac]Implement ViewID support. (third approach)

chrome/browser/cocoa/bookmark_button.mm

Index: chrome/browser/cocoa/bookmark_button.mm
diff --git a/chrome/browser/cocoa/bookmark_button.mm b/chrome/browser/cocoa/bookmark_button.mm
index 00a6b775c82cfe0be9d7406e132acf2802a71b6c..bfacc8fec333f7cb1fb9c291631a7549234bdc4a 100644
--- a/chrome/browser/cocoa/bookmark_button.mm
+++ b/chrome/browser/cocoa/bookmark_button.mm
@@ -8,6 +8,7 @@
 #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;
@@ -24,6 +25,20 @@ static const CGFloat kDragImageOpacity = 0.7;
 
 @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];
 }