Unuse bitfields for ElementRareData::m_proxyCount.

Source/core/dom/ElementRareData.h

Index: Source/core/dom/ElementRareData.h
diff --git a/Source/core/dom/ElementRareData.h b/Source/core/dom/ElementRareData.h
index 5f998e1a175df798dd48a5342cb1e2fa5b20f95f..bcd739cf05d7d796782502e1998914bdb2390157 100644
--- a/Source/core/dom/ElementRareData.h
+++ b/Source/core/dom/ElementRareData.h
@@ -129,7 +129,9 @@ public:
 
 private:
     short m_tabindex;
-    unsigned short m_proxyCount : 10;
+    // As m_proxyCount usually doesn't exceed 10bits (1024), if you want to add some booleans you
+    // can steal some bits from m_proxyCount by using bitfields to prevent ElementRareData bloat.
+    unsigned short m_proxyCount;
 
     LayoutSize m_minimumSizeForResizing;
     IntSize m_savedLayerScrollOffset;