[Mac]Implement ViewID support. (third approach)

chrome/browser/cocoa/tab_view.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/tab_view.h"
 
 #include "base/logging.h"
 #import "base/mac_util.h"
 #include "base/nsimage_cache_mac.h"
 #include "base/scoped_cftyperef.h"
 #include "chrome/browser/browser_theme_provider.h"
 #import "chrome/browser/cocoa/tab_controller.h"
 #import "chrome/browser/cocoa/tab_window_controller.h"
 #import "chrome/browser/cocoa/themed_window.h"
+#import "chrome/browser/cocoa/view_id_util.h"
 #include "grit/theme_resources.h"
 
 namespace {
 
 // Constants for inset and control points for tab shape.
 const CGFloat kInsetMultiplier = 2.0/3.0;
 const CGFloat kControlPoint1Multiplier = 1.0/3.0;
 const CGFloat kControlPoint2Multiplier = 3.0/8.0;
 
 // The amount of time in seconds during which each type of glow increases, holds
@@ skipping 998 matching lines @@
     } else {
       NOTREACHED();
     }
   }
   if (useCache) {
     workspaceIDCache_[windowID] = workspace;
   }
   return workspace;
 }
 
+- (ViewID)viewID {
+  return VIEW_ID_TAB;
+}
+
 @end  // @implementation TabView(Private)