compositor-worker: Force elements to grow a layer when a CompositorProxy is created.

Source/core/style/StyleRareNonInheritedData.h

Index: Source/core/style/StyleRareNonInheritedData.h
diff --git a/Source/core/style/StyleRareNonInheritedData.h b/Source/core/style/StyleRareNonInheritedData.h
index 7b39768e741682a3048472ec2327daba850944e2..3ec7a162804b23325a0c85a3926049197dc59d8c 100644
--- a/Source/core/style/StyleRareNonInheritedData.h
+++ b/Source/core/style/StyleRareNonInheritedData.h
@@ -209,6 +209,7 @@ public:
     // Whether the transform (if it exists) is stored in the element's inline style.
     unsigned m_hasInlineTransform : 1;
     unsigned m_resize : 2; // EResize
+    unsigned m_hasCompositorProxy : 1;
 
 private:
     StyleRareNonInheritedData();