Don't repaint tab when TabRenderData hasn't changed.

chrome/browser/ui/views/tabs/tab_renderer_data.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_VIEWS_TABS_TAB_RENDERER_DATA_H_
 #define CHROME_BROWSER_UI_VIEWS_TABS_TAB_RENDERER_DATA_H_
 #pragma once
 
 #include "base/process_util.h"
 #include "base/string16.h"
@@ skipping 23 matching lines @@
 
   // This interprets the crashed status to decide whether or not this
   // render data represents a tab that is "crashed" (i.e. the render
   // process died unexpectedly).
   bool IsCrashed() const {
     return (crashed_status == base::TERMINATION_STATUS_PROCESS_WAS_KILLED ||
             crashed_status == base::TERMINATION_STATUS_PROCESS_CRASHED ||
             crashed_status == base::TERMINATION_STATUS_ABNORMAL_TERMINATION);
   }
 
+  // Returns true if the TabRendererData is same as given |data|. Two favicons
+  // are considered equals if two SkBitmaps point to the same SkPixelRef object.
+  bool Equals(const TabRendererData& data) {
+    return
+        favicon.pixelRef() &&
+        favicon.pixelRef() == data.favicon.pixelRef() &&
+        favicon.pixelRefOffset() == data.favicon.pixelRefOffset() &&

[oshima, 2011/02/26 00:18:29]

Brett, I'm assuming that chrome does not change
the data in SkPixelRef for favicons. Scott told me that you may know if my
assumption is correct. Let me know if you don't know and I'll find someone else.

[brettw, 2011/02/26 03:26:04]

Good question. This is *probably* OK but I'm not sure. I'm adding Mike Reed to
the review who will be able to tell us definitively.

+        network_state == data.network_state &&
+        title == data.title &&
+        loading == data.loading &&
+        crashed_status == data.crashed_status &&
+        off_the_record == data.off_the_record &&
+        show_icon == data.show_icon &&
+        mini == data.mini &&
+        blocked == data.blocked &&
+        app == data.app;
+  }
+
   SkBitmap favicon;
   NetworkState network_state;
   string16 title;
   bool loading;
   base::TerminationStatus crashed_status;
   bool off_the_record;
   bool show_icon;
   bool mini;
   bool blocked;
   bool app;
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_TABS_TAB_RENDERER_DATA_H_