Oilpan: eagerly finalize WebGLRenderingContext objects.

Source/core/html/canvas/WebGLObject.h

Index: Source/core/html/canvas/WebGLObject.h
diff --git a/Source/core/html/canvas/WebGLObject.h b/Source/core/html/canvas/WebGLObject.h
index b94a612ac520223a92efd7ca629d9687bc87fec6..adb03b588ecfaac3af1061b821cc6fdffbe7bbc8 100644
--- a/Source/core/html/canvas/WebGLObject.h
+++ b/Source/core/html/canvas/WebGLObject.h
@@ -61,7 +61,7 @@ public:
     // This indicates whether the client side issue a delete call already, not
     // whether the OpenGL resource is deleted.
     // object()==0 indicates the OpenGL resource is deleted.
-    bool isDeleted() { return m_deleted; }
+    bool isDeleted() const { return m_deleted; }
 
     // True if this object belongs to the group or context.
     virtual bool validate(const WebGLContextGroup*, const WebGLRenderingContextBase*) const = 0;