cc: Don't use partial updates for scrollbars when they are not allowed.

cc/scrollbar_layer.h

 // Copyright 2012 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 CC_SCROLLBAR_LAYER_H_
 #define CC_SCROLLBAR_LAYER_H_
 
 #include "cc/caching_bitmap_content_layer_updater.h"
 #include "cc/cc_export.h"
@@ skipping 40 matching lines @@
         scoped_ptr<ScrollbarThemePainter>,
         scoped_ptr<WebKit::WebScrollbarThemeGeometry>,
         int scrollLayerId);
     virtual ~ScrollbarLayer();
 
 private:
     void updatePart(CachingBitmapContentLayerUpdater*, LayerUpdater::Resource*, const gfx::Rect&, ResourceUpdateQueue&, RenderingStats&);
     void createUpdaterIfNeeded();
     gfx::Rect scrollbarLayerRectToContentRect(const gfx::Rect& layerRect) const;
 
+    bool isDirty() const { return !m_dirtyRect.IsEmpty(); }
+
     int maxTextureSize();
     float clampScaleToMaxTextureSize(float scale);
 
     scoped_ptr<WebKit::WebScrollbar> m_scrollbar;
     scoped_ptr<ScrollbarThemePainter> m_painter;
     scoped_ptr<WebKit::WebScrollbarThemeGeometry> m_geometry;
     int m_scrollLayerId;
 
     GLenum m_textureFormat;
 
+    gfx::RectF m_dirtyRect;
+
     scoped_refptr<CachingBitmapContentLayerUpdater> m_backTrackUpdater;
     scoped_refptr<CachingBitmapContentLayerUpdater> m_foreTrackUpdater;
     scoped_refptr<CachingBitmapContentLayerUpdater> m_thumbUpdater;
 
     // All the parts of the scrollbar except the thumb
     scoped_ptr<LayerUpdater::Resource> m_backTrack;
     scoped_ptr<LayerUpdater::Resource> m_foreTrack;
     scoped_ptr<LayerUpdater::Resource> m_thumb;
 };
 
 }
 #endif  // CC_SCROLLBAR_LAYER_H_