Make WebGL extensions get lost when context is lost.

Source/core/html/canvas/EXTTextureFilterAnisotropic.h

Index: Source/core/html/canvas/EXTTextureFilterAnisotropic.h
diff --git a/Source/core/html/canvas/EXTTextureFilterAnisotropic.h b/Source/core/html/canvas/EXTTextureFilterAnisotropic.h
index 7daafd9911d03ee1e1d09ebab60efa74e7b4ccf5..6c445f9745edf05eafb2a75051f6ec9c3d7b9791 100644
--- a/Source/core/html/canvas/EXTTextureFilterAnisotropic.h
+++ b/Source/core/html/canvas/EXTTextureFilterAnisotropic.h
@@ -28,13 +28,13 @@
 
 #include "bindings/v8/ScriptWrappable.h"
 #include "core/html/canvas/WebGLExtension.h"
-#include "wtf/PassOwnPtr.h"
+#include "wtf/PassRefPtr.h"
 
 namespace WebCore {
 
 class EXTTextureFilterAnisotropic : public WebGLExtension, public ScriptWrappable {
 public:
-    static PassOwnPtr<EXTTextureFilterAnisotropic> create(WebGLRenderingContext*);
+    static PassRefPtr<EXTTextureFilterAnisotropic> create(WebGLRenderingContext*);
     static bool supported(WebGLRenderingContext*);
     static const char* getExtensionName();