Use recomputed interest rect only if it changed enough

third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp

 /*
  * Copyright (C) 2009, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 782 matching lines @@
     IntRect transformedClip = clip;
     transformedClip.moveBy(paintOffset);
 
     AffineTransform translation;
     translation.translate(-paintOffset.x(), -paintOffset.y());
     TransformRecorder transformRecorder(context, *scrollbar, translation);
 
     scrollbar->paint(&context, CullRect(transformedClip));
 }
 
-void PaintLayerCompositor::paintContents(const GraphicsLayer* graphicsLayer, GraphicsContext& context, GraphicsLayerPaintingPhase, const IntRect* clip) const
+IntRect PaintLayerCompositor::computeInterestRect(const GraphicsLayer* graphicsLayer, const IntRect&) const
 {
-    IntRect defaultClip;
-    if (RuntimeEnabledFeatures::slimmingPaintSynchronizedPaintingEnabled() && !clip) {
-        defaultClip.setSize(m_layoutView.layoutSize(IncludeScrollbars));
-        clip = &defaultClip;
-    }
-    ASSERT(clip);
+    return IntRect(IntPoint(), m_layoutView.layoutSize(IncludeScrollbars));
+}
 
+void PaintLayerCompositor::paintContents(const GraphicsLayer* graphicsLayer, GraphicsContext& context, GraphicsLayerPaintingPhase, const IntRect& interestRect) const
+{
     if (graphicsLayer == layerForHorizontalScrollbar())
-        paintScrollbar(m_layoutView.frameView()->horizontalScrollbar(), context, *clip);
+        paintScrollbar(m_layoutView.frameView()->horizontalScrollbar(), context, interestRect);
     else if (graphicsLayer == layerForVerticalScrollbar())
-        paintScrollbar(m_layoutView.frameView()->verticalScrollbar(), context, *clip);
+        paintScrollbar(m_layoutView.frameView()->verticalScrollbar(), context, interestRect);
     else if (graphicsLayer == layerForScrollCorner())
-        FramePainter(*m_layoutView.frameView()).paintScrollCorner(&context, *clip);
+        FramePainter(*m_layoutView.frameView()).paintScrollCorner(&context, interestRect);
 }
 
 bool PaintLayerCompositor::supportsFixedRootBackgroundCompositing() const
 {
     if (Settings* settings = m_layoutView.document().settings())
         return settings->preferCompositingToLCDTextEnabled();
     return false;
 }
 
 bool PaintLayerCompositor::needsFixedRootBackgroundLayer(const PaintLayer* layer) const
@@ skipping 349 matching lines @@
 Page* PaintLayerCompositor::page() const
 {
     return m_layoutView.frameView()->frame().page();
 }
 
 DocumentLifecycle& PaintLayerCompositor::lifecycle() const
 {
     return m_layoutView.document().lifecycle();
 }
 
-String PaintLayerCompositor::debugName(const GraphicsLayer* graphicsLayer)
+String PaintLayerCompositor::debugName(const GraphicsLayer* graphicsLayer) const
 {
     String name;
     if (graphicsLayer == m_rootContentLayer.get()) {
         name = "Content Root Layer";
     } else if (graphicsLayer == m_rootTransformLayer.get()) {
         name = "Root Transform Layer";
     } else if (graphicsLayer == m_overflowControlsHostLayer.get()) {
         name = "Frame Overflow Controls Host Layer";
     } else if (graphicsLayer == m_layerForHorizontalScrollbar.get()) {
         name = "Frame Horizontal Scrollbar Layer";
     } else if (graphicsLayer == m_layerForVerticalScrollbar.get()) {
         name = "Frame Vertical Scrollbar Layer";
     } else if (graphicsLayer == m_layerForScrollCorner.get()) {
         name = "Frame Scroll Corner Layer";
     } else if (graphicsLayer == m_containerLayer.get()) {
         name = "Frame Clipping Layer";
     } else if (graphicsLayer == m_scrollLayer.get()) {
         name = "Frame Scrolling Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace blink