Use recomputed interest rect only if it changed enough

third_party/WebKit/Source/platform/graphics/GraphicsLayer.cpp

Index: third_party/WebKit/Source/platform/graphics/GraphicsLayer.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/GraphicsLayer.cpp b/third_party/WebKit/Source/platform/graphics/GraphicsLayer.cpp
index 4d51cb8a53798cfdf7b835e5a4b01253204fe94c..ac53903d44f3a4cdf1f81209f92cdb4922cf92b7 100644
--- a/third_party/WebKit/Source/platform/graphics/GraphicsLayer.cpp
+++ b/third_party/WebKit/Source/platform/graphics/GraphicsLayer.cpp
@@ -293,9 +293,9 @@ void GraphicsLayer::setOffsetDoubleFromLayoutObject(const DoubleSize& offset, Sh
         setNeedsDisplay();
 }
 
-void GraphicsLayer::paint(GraphicsContext& context, const IntRect* clip)
+void GraphicsLayer::paint(GraphicsContext& context, const IntRect* interestRect)
 {
-    ASSERT(clip || RuntimeEnabledFeatures::slimmingPaintSynchronizedPaintingEnabled());
+    ASSERT(interestRect || RuntimeEnabledFeatures::slimmingPaintSynchronizedPaintingEnabled());
     ASSERT(drawsContent());
 
     if (!m_client)
@@ -312,7 +312,7 @@ void GraphicsLayer::paint(GraphicsContext& context, const IntRect* clip)
         }
     }
 #endif
-    m_client->paintContents(this, context, m_paintingPhase, clip);
+    m_previousInterestRect = m_client->paintContents(this, context, m_paintingPhase, interestRect);
     notifyFirstPaintToClient();
 }