Make WebGL extensions get lost when context is lost.

Source/core/html/canvas/WebGLCompressedTextureS3TC.h

Index: Source/core/html/canvas/WebGLCompressedTextureS3TC.h
diff --git a/Source/core/html/canvas/WebGLCompressedTextureS3TC.h b/Source/core/html/canvas/WebGLCompressedTextureS3TC.h
index 24a1d57847a8984f7b2b2490ee5739c47729bd4d..b8816bef3cc0bccd58b043efec252bc70c692f9a 100644
--- a/Source/core/html/canvas/WebGLCompressedTextureS3TC.h
+++ b/Source/core/html/canvas/WebGLCompressedTextureS3TC.h
@@ -29,7 +29,7 @@
 #include "bindings/v8/ScriptWrappable.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/html/canvas/WebGLExtension.h"
-#include "wtf/PassOwnPtr.h"
+#include "wtf/PassRefPtr.h"
 
 namespace WebCore {
 
@@ -37,7 +37,7 @@ class WebGLTexture;
 
 class WebGLCompressedTextureS3TC : public WebGLExtension, public ScriptWrappable {
 public:
-    static PassOwnPtr<WebGLCompressedTextureS3TC> create(WebGLRenderingContext*);
+    static PassRefPtr<WebGLCompressedTextureS3TC> create(WebGLRenderingContext*);
     static bool supported(WebGLRenderingContext*);
     static const char* getExtensionName();