Reduce texture uploads during scrollbar invalidations.

cc/ScrollbarLayerChromium.cpp

 // 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.
 
 #include "config.h"
 
 #if USE(ACCELERATED_COMPOSITING)
 
 #include "ScrollbarLayerChromium.h"
 
 #include "base/basictypes.h"
 #include "BitmapCanvasLayerTextureUpdater.h"
+#include "caching_bitmap_canvas_layer_texture_updater.h"
 #include "CCLayerTreeHost.h"
 #include "CCScrollbarLayerImpl.h"
 #include "CCTextureUpdateQueue.h"
 #include "LayerPainterChromium.h"
 #include <public/WebRect.h>
 
 using WebKit::WebRect;
 
 namespace cc {
 
@@ skipping 163 matching lines @@
     }
 
     LayerChromium::setLayerTreeHost(host);
 }
 
 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());
 }
 
 void ScrollbarLayerChromium::updatePart(LayerTextureUpdater* painter, LayerTextureUpdater::Texture* texture, const IntRect& rect, CCTextureUpdateQueue& queue, CCRenderingStats& stats)
 {
     // Skip painting and uploading if there are no invalidations and
     // we already have valid texture data.
     if (texture->texture()->haveBackingTexture()
             && texture->texture()->size() == rect.size()
             && m_updateRect.isEmpty())
         return;
 
     // We should always have enough memory for UI.
     ASSERT(texture->texture()->canAcquireBackingTexture());
     if (!texture->texture()->canAcquireBackingTexture())
         return;
 
     // Paint and upload the entire part.
     float widthScale = static_cast<float>(contentBounds().width()) / bounds().width();
     float heightScale = static_cast<float>(contentBounds().height()) / bounds().height();
     IntRect paintedOpaqueRect;
     painter->prepareToUpdate(rect, rect.size(), widthScale, heightScale, paintedOpaqueRect, stats);
+    if (!painter->pixelsDidChange() && texture->texture()->haveBackingTexture())
+        return;
+
     texture->prepareRect(rect, stats);
 
     IntSize destOffset(0, 0);
     TextureUploader::Parameters upload = { texture, rect, destOffset };
     queue.appendFullUpload(upload);
 }
 
 
 void ScrollbarLayerChromium::setTexturePriorities(const CCPriorityCalculator&)
 {
@@ skipping 33 matching lines @@
 
     // Consider the thumb to be at the origin when painting.
     WebKit::WebRect thumbRect = m_geometry->thumbRect(m_scrollbar.get());
     IntRect originThumbRect = layerRectToContentRect(WebKit::WebRect(0, 0, thumbRect.width, thumbRect.height));
     if (!originThumbRect.isEmpty())
         updatePart(m_thumbUpdater.get(), m_thumb.get(), originThumbRect, queue, stats);
 }
 
 }
 #endif // USE(ACCELERATED_COMPOSITING)