compositor-worker: Introduce CompositorProxy::disconnect().

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 82ea814f7851062f74b4e1fd11cf0fa38c969ba1..9453d8d83164578c7eadb2860c81aef00b6f47eb 100644
--- a/Source/core/dom/ElementRareData.h
+++ b/Source/core/dom/ElementRareData.h
@@ -123,6 +123,14 @@ public:
     bool hasPseudoElements() const;
     void clearPseudoElements();
 
+    uint32_t incrementProxyCount() { return ++m_proxyCount; }
+    uint32_t decrementProxyCount()
+    {
+        ASSERT(m_proxyCount);
+        return --m_proxyCount;
+    }
+    uint32_t proxyCount() const { return m_proxyCount; }
+
     void setCustomElementDefinition(PassRefPtrWillBeRawPtr<CustomElementDefinition> definition) { m_customElementDefinition = definition; }
     CustomElementDefinition* customElementDefinition() const { return m_customElementDefinition.get(); }
 
@@ -135,6 +143,7 @@ public:
 private:
     short m_tabindex;
     bool m_tabStop;
+    uint32_t m_proxyCount;

[esprehn, 2015/04/09 05:14:55]

Do you really need 32 bits worth of these? This is huge. There's probably some
free bits in there, use some of those.

[sadrul, 2015/04/09 16:19:33]

Would it make sense to use a short (unsigned?) instead? (NodeRareData has only 2
unused bits, not enough to be useful for this).

[sadrul, 2015/04/09 16:41:09]

Aha! I wasn't looking hard enough. NodeRareData doesn't have enough unused bits,
but ElementRareData does. I have made this change in the latest patchset (and
limited the proxy-count to 10 bits). The size of the ElementRareData does not
need to increase anymore because of this change, and there are still some unused
bits we could use for other purposes (or for proxy-count if we need to).

 
     LayoutSize m_minimumSizeForResizing;
     IntSize m_savedLayerScrollOffset;
@@ -168,6 +177,7 @@ inline ElementRareData::ElementRareData(LayoutObject* renderer)
     : NodeRareData(renderer)
     , m_tabindex(0)
     , m_tabStop(true)
+    , m_proxyCount(0)
     , m_minimumSizeForResizing(defaultMinimumSizeForResizing())
 {
     m_isElementRareData = true;