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

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

Index: third_party/WebKit/Source/core/paint/PaintLayer.h
diff --git a/third_party/WebKit/Source/core/paint/PaintLayer.h b/third_party/WebKit/Source/core/paint/PaintLayer.h
index 7cab7a2fd1bbb3bcda8c4131cd0dfdde87f8edae..264c5cfd584983ebd90cdce4744574b71b2b8214 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.h
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.h
@@ -241,6 +241,10 @@ public:
     // FIXME: Many people call this function while it has out-of-date information.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;
+
     bool isTransparent() const { return layoutObject()->isTransparent() || layoutObject()->style()->hasBlendMode() || layoutObject()->hasMask(); }
 
     bool isReflection() const { return layoutObject()->isReplica(); }
@@ -791,6 +795,8 @@ private:
         m_needsPaintPhaseDescendantBlockBackgrounds |= layer.m_needsPaintPhaseDescendantBlockBackgrounds;
     }
 
+    bool isSelfPaintingLayerForIntrinsicOrScrollingReasons() const;
+
     bool shouldFragmentCompositedBounds(const PaintLayer* compositingLayer) const;
 
     // Self-painting layer is an optimization where we avoid the heavy Layer painting