[Mac]Implement ViewID support.

chrome/browser/cocoa/base_view.mm

-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// 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.
 
-#include "chrome/browser/cocoa/base_view.h"
+#import "chrome/browser/cocoa/base_view.h"
+#import "chrome/browser/cocoa/view_id_util.h"
 
 @implementation BaseView
 
+@synthesize viewID = viewID_;
+
 - (id)initWithFrame:(NSRect)frame {
   self = [super initWithFrame:frame];
   if (self) {
     trackingArea_ =
         [[NSTrackingArea alloc] initWithRect:frame
                                      options:NSTrackingMouseMoved |
                                              NSTrackingMouseEnteredAndExited |
                                              NSTrackingActiveInActiveApp |
                                              NSTrackingInVisibleRect
                                        owner:self
@@ skipping 114 matching lines @@
   return new_rect;
 }
 
 - (NSRect)RectToNSRect:(gfx::Rect)rect {
   NSRect new_rect(NSRectFromCGRect(rect.ToCGRect()));
   new_rect.origin.y =
       [self bounds].size.height - new_rect.origin.y - new_rect.size.height;
   return new_rect;
 }
 
+// We use NSView's tag prooperty for ViewID support. Subclasses should not
+// override it for other purpose.
+- (NSInteger)tag {
+  return view_id_util::ViewIDToTag(viewID_);
+}
+
 @end