Add a hack to set shouldPaint to true for force-composited iframes.

third_party/WebKit/Source/core/paint/PaintLayer.h

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
@@ skipping 221 matching lines @@
     PaintLayer* removeChild(PaintLayer*);
 
     void removeOnlyThisLayerAfterStyleChange();
     void insertOnlyThisLayerAfterStyleChange();
 
     void styleDidChange(StyleDifference, const ComputedStyle* oldStyle);
 
     // FIXME: Many people call this function while it has out-of-date information.
     bool isSelfPaintingLayer() const { return m_isSelfPaintingLayer; }
 
+    // PaintLayers which represent LayoutParts may become self-painting due to being composited.
+    // If this is the case, this method returns true.
+    bool isSelfPaintingOnlyBecauseIsCompositedPart() const;
+
     void setLayerType(PaintLayerType layerType) { m_layerType = layerType; ASSERT(static_cast<PaintLayerType>(m_layerType) == layerType); }
 
     bool isTransparent() const { return layoutObject()->isTransparent() || layoutObject()->style()->hasBlendMode() || layoutObject()->hasMask(); }
 
     bool isReflection() const { return layoutObject()->isReplica(); }
     PaintLayerReflectionInfo* reflectionInfo() { return m_rareData ? m_rareData->reflectionInfo.get() : nullptr; }
     const PaintLayerReflectionInfo* reflectionInfo() const { return const_cast<PaintLayer*>(this)->reflectionInfo(); }
 
     const PaintLayer* root() const
     {
@@ skipping 527 matching lines @@
         return *m_rareData;
     }
 
     void mergeNeedsPaintPhaseFlagsFrom(const PaintLayer& layer)
     {
         m_needsPaintPhaseDescendantOutlines |= layer.m_needsPaintPhaseDescendantOutlines;
         m_needsPaintPhaseFloat |= layer.m_needsPaintPhaseFloat;
         m_needsPaintPhaseDescendantBlockBackgrounds |= layer.m_needsPaintPhaseDescendantBlockBackgrounds;
     }
 
+    bool isSelfPaintingLayerForIntrinsicOrScrollingReasons() const;
+
     unsigned m_layerType : 2; // PaintLayerType
 
     // Self-painting layer is an optimization where we avoid the heavy Layer painting
     // machinery for a Layer allocated only to handle the overflow clip case.
     // FIXME(crbug.com/332791): Self-painting layer should be merged into the overflow-only concept.
     unsigned m_isSelfPaintingLayer : 1;
 
     // If have no self-painting descendants, we don't have to walk our children during painting. This can lead to
     // significant savings, especially if the tree has lots of non-self-painting layers grouped together (e.g. table cells).
     mutable unsigned m_hasSelfPaintingLayerDescendant : 1;
@@ skipping 93 matching lines @@
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showLayerTree(const blink::PaintLayer*);
 void showLayerTree(const blink::LayoutObject*);
 #endif
 
 #endif // Layer_h