Track scissored damage area for WebGL

Source/platform/graphics/GraphicsLayer.cpp

Index: Source/platform/graphics/GraphicsLayer.cpp
diff --git a/Source/platform/graphics/GraphicsLayer.cpp b/Source/platform/graphics/GraphicsLayer.cpp
index f2d1d39a71c7de19ea74612b701d63661e02eb29..ced35e76cd6599f96026ea78d2ef0963d360c365 100644
--- a/Source/platform/graphics/GraphicsLayer.cpp
+++ b/Source/platform/graphics/GraphicsLayer.cpp
@@ -890,11 +890,14 @@ void GraphicsLayer::setIsRootForIsolatedGroup(bool isolated)
     platformLayer()->setIsRootForIsolatedGroup(isolated);
 }
 
-void GraphicsLayer::setContentsNeedsDisplay()
+void GraphicsLayer::setContentsNeedsDisplay(const IntRect& dirtyRect)
 {
     if (WebLayer* contentsLayer = contentsLayerIfRegistered()) {
-        contentsLayer->invalidate();
-        addRepaintRect(m_contentsRect);
+        IntRect rect = m_contentsRect;
+        if (!dirtyRect.isEmpty())
+            rect = dirtyRect;
+        contentsLayer->invalidateRect(rect);
+        addRepaintRect(rect);
     }
 }