Reduce texture uploads during scrollbar invalidations.

cc/ScrollbarLayerChromium.cpp

Index: cc/ScrollbarLayerChromium.cpp
diff --git a/cc/ScrollbarLayerChromium.cpp b/cc/ScrollbarLayerChromium.cpp
index 4f3a09fa5e47e6f2b4ff938adb24fb727fbff76d..423deed1014733a7dfbc41a3684c7aa2f0e0d719 100644
--- a/cc/ScrollbarLayerChromium.cpp
+++ b/cc/ScrollbarLayerChromium.cpp
@@ -10,6 +10,7 @@
 
 #include "base/basictypes.h"
 #include "BitmapCanvasLayerTextureUpdater.h"
+#include "caching_bitmap_canvas_layer_texture_updater.h"
 #include "CCLayerTreeHost.h"
 #include "CCScrollbarLayerImpl.h"
 #include "CCTextureUpdateQueue.h"
@@ -193,20 +194,20 @@ void ScrollbarLayerChromium::createTextureUpdaterIfNeeded()
     m_textureFormat = layerTreeHost()->rendererCapabilities().bestTextureFormat;
 
     if (!m_backTrackUpdater)
-        m_backTrackUpdater = BitmapCanvasLayerTextureUpdater::create(ScrollbarBackgroundPainter::create(m_scrollbar.get(), m_painter, m_geometry.get(), WebKit::WebScrollbar::BackTrackPart));
+        m_backTrackUpdater = CachingBitmapCanvasLayerTextureUpdater::create(ScrollbarBackgroundPainter::create(m_scrollbar.get(), m_painter, m_geometry.get(), WebKit::WebScrollbar::BackTrackPart));
     if (!m_backTrack)
         m_backTrack = m_backTrackUpdater->createTexture(layerTreeHost()->contentsTextureManager());
 
     // Only create two-part track if we think the two parts could be different in appearance.
     if (m_scrollbar->isCustomScrollbar()) {
         if (!m_foreTrackUpdater)
-            m_foreTrackUpdater = BitmapCanvasLayerTextureUpdater::create(ScrollbarBackgroundPainter::create(m_scrollbar.get(), m_painter, m_geometry.get(), WebKit::WebScrollbar::ForwardTrackPart));
+            m_foreTrackUpdater = CachingBitmapCanvasLayerTextureUpdater::create(ScrollbarBackgroundPainter::create(m_scrollbar.get(), m_painter, m_geometry.get(), WebKit::WebScrollbar::ForwardTrackPart));
         if (!m_foreTrack)
             m_foreTrack = m_foreTrackUpdater->createTexture(layerTreeHost()->contentsTextureManager());
     }
 
     if (!m_thumbUpdater)
-        m_thumbUpdater = BitmapCanvasLayerTextureUpdater::create(ScrollbarThumbPainter::create(m_scrollbar.get(), m_painter, m_geometry.get()));
+        m_thumbUpdater = CachingBitmapCanvasLayerTextureUpdater::create(ScrollbarThumbPainter::create(m_scrollbar.get(), m_painter, m_geometry.get()));
     if (!m_thumb)
         m_thumb = m_thumbUpdater->createTexture(layerTreeHost()->contentsTextureManager());
 }