Implement WEBGL_shared_resources

Source/core/html/canvas/WebGLContextGroup.h

Index: Source/core/html/canvas/WebGLContextGroup.h
diff --git a/Source/core/html/canvas/WebGLContextGroup.h b/Source/core/html/canvas/WebGLContextGroup.h
index e888083f38fd8bcf2064758872fc00d3cf686e0f..1d2bc7738e21c479554a635e07653fd17b49bc6c 100644
--- a/Source/core/html/canvas/WebGLContextGroup.h
+++ b/Source/core/html/canvas/WebGLContextGroup.h
@@ -45,6 +45,7 @@ public:
     static PassRefPtr<WebGLContextGroup> create();
     virtual ~WebGLContextGroup();
 
+    // Adds the context to this group.
     void addContext(WebGLRenderingContext*);
     void removeContext(WebGLRenderingContext*);
 
@@ -55,6 +56,8 @@ public:
 
     void loseContextGroup(WebGLRenderingContext::LostContextMode);
 
+    void cancelAcquireSharedResource(const WebGLRenderingContext*, long);
+
   private:
     friend class WebGLObject;
 
@@ -62,6 +65,8 @@ public:
 
     void detachAndRemoveAllObjects();
 
+    long m_acquireRequestCount;
+
     HashSet<WebGLRenderingContext*> m_contexts;
     HashSet<WebGLSharedObject*> m_groupObjects;
 };