Suppress layer creation for descendants of GPU-rasterized layers

Source/core/rendering/RenderLayer.h

Index: Source/core/rendering/RenderLayer.h
diff --git a/Source/core/rendering/RenderLayer.h b/Source/core/rendering/RenderLayer.h
index c02a990249c859e8d7fc50be5ea9ccd54a3eb895..1cfdc227d68395f105ca2b75711c07383dc2982f 100644
--- a/Source/core/rendering/RenderLayer.h
+++ b/Source/core/rendering/RenderLayer.h
@@ -504,6 +504,9 @@ public:
     bool shouldIsolateCompositedDescendants() const { return m_compositingProperties.shouldIsolateCompositedDescendants; }
     void setShouldIsolateCompositedDescendants(bool b)  { m_compositingProperties.shouldIsolateCompositedDescendants = b; }
 
+    bool suppressingCompositedLayerCreation() const { return m_compositingProperties.suppressingCompositedLayerCreation; }
+    void setSuppressingCompositedLayerCreation(bool b) { m_compositingProperties.suppressingCompositedLayerCreation = b; }
+
     void updateDescendantDependentFlags();
 
     void updateOrRemoveFilterEffectRenderer();
@@ -728,6 +731,7 @@ private:
             , lostGroupedMapping(false)
             , viewportConstrainedNotCompositedReason(NoNotCompositedReason)
             , compositingReasons(CompositingReasonNone)
+            , suppressingCompositedLayerCreation(false)
         { }
 
         // Used only while determining what layers should be composited. Applies to the tree of z-order lists.
@@ -752,6 +756,9 @@ private:
 
         // Used for invalidating this layer's contents on the squashing GraphicsLayer.
         IntSize offsetFromSquashingLayerOrigin;
+
+        // Whether this render layer is trying to avoid becoming composited, if possible.
+        bool suppressingCompositedLayerCreation : 1;
     };
 
     AncestorDependentProperties m_ancestorDependentProperties;