Remove the clip argument to WebContentLayerClient::paintContents.

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

 /*
  * Copyright (C) 2009 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 284 matching lines @@
         setNeedsDisplay();
 }
 
 IntRect GraphicsLayer::interestRect()
 {
     if (!RuntimeEnabledFeatures::slimmingPaintSynchronizedPaintingEnabled())
         m_previousInterestRect = m_client->computeInterestRect(this, m_previousInterestRect);
     return m_previousInterestRect;
 }
 
 void GraphicsLayer::paint(GraphicsContext& context, const IntRect* interestRect)

[jbroman, 2015/12/01 21:11:02]

Is the plan to ultimately remove the argument from this method too? I can't tell
from either GraphicsLayer or GraphicsContextPainter what the conditions are
where one should expect this to be provided and where it should be null.

 {
-    ASSERT(interestRect || RuntimeEnabledFeatures::slimmingPaintSynchronizedPaintingEnabled());
     ASSERT(drawsContent());
     ASSERT(&context.paintController() == m_paintController);
 
     if (!m_client)
         return;
     if (firstPaintInvalidationTrackingEnabled())
         m_debugInfo.clearAnnotatedInvalidateRects();
     incrementPaintCount();
 
     IntRect newInterestRect;
+    if (!interestRect) {
+        newInterestRect = m_client->computeInterestRect(this, m_previousInterestRect);
+        interestRect = &newInterestRect;
+    }
+
     if (RuntimeEnabledFeatures::slimmingPaintSynchronizedPaintingEnabled()) {
-        if (!interestRect) {
-            newInterestRect = m_client->computeInterestRect(this, m_previousInterestRect);
-            interestRect = &newInterestRect;
-        }
         if (!m_client->needsRepaint() && !paintController()->cacheIsEmpty() && m_previousInterestRect == *interestRect) {
             paintController()->createAndAppend<CachedDisplayItem>(*this, DisplayItem::CachedDisplayItemList);
             return;
         }
     }
 
 #ifndef NDEBUG
     if (contentsOpaque() && s_drawDebugRedFill) {
         FloatRect rect(FloatPoint(), size());
         if (!DrawingRecorder::useCachedDrawingIfPossible(context, *this, DisplayItem::DebugRedFill)) {
@@ skipping 889 matching lines @@
 {
     if (!layer) {
         fprintf(stderr, "Cannot showGraphicsLayerTree for (nil).\n");
         return;
     }
 
     String output = layer->layerTreeAsText(blink::LayerTreeIncludesDebugInfo);
     fprintf(stderr, "%s\n", output.utf8().data());
 }
 #endif