Use recomputed interest rect only if it changed enough

third_party/WebKit/Source/web/PageOverlay.cpp

Index: third_party/WebKit/Source/web/PageOverlay.cpp
diff --git a/third_party/WebKit/Source/web/PageOverlay.cpp b/third_party/WebKit/Source/web/PageOverlay.cpp
index 86ae8472837d8a49b0b163c48c71e5694fc616f1..06e086f95e143877fec7acf045f3e589f21f5216 100644
--- a/third_party/WebKit/Source/web/PageOverlay.cpp
+++ b/third_party/WebKit/Source/web/PageOverlay.cpp
@@ -96,10 +96,12 @@ void PageOverlay::update()
     m_layer->setNeedsDisplay();
 }
 
-void PageOverlay::paintContents(const GraphicsLayer* graphicsLayer, GraphicsContext& gc, GraphicsLayerPaintingPhase phase, const IntRect* inClip) const
+IntRect PageOverlay::paintContents(const GraphicsLayer* graphicsLayer, GraphicsContext& gc, GraphicsLayerPaintingPhase phase, const IntRect*) const
 {
     ASSERT(m_layer);
-    m_delegate->paintPageOverlay(*this, gc, expandedIntSize(m_layer->size()));
+    IntSize paintSize = expandedIntSize(m_layer->size());
+    m_delegate->paintPageOverlay(*this, gc, paintSize);
+    return IntRect(IntPoint(), paintSize);
 }
 
 String PageOverlay::debugName(const GraphicsLayer*)