Make WebGL2 objects Oilpan compatible.

Source/core/html/canvas/WebGL2RenderingContext.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef WebGL2RenderingContext_h
 #define WebGL2RenderingContext_h
 
 #include "core/html/canvas/WebGL2RenderingContextBase.h"
 
 namespace blink {
 
 class WebGL2RenderingContext : public WebGL2RenderingContextBase {
     DEFINE_WRAPPERTYPEINFO();
 public:
     static PassOwnPtrWillBeRawPtr<WebGL2RenderingContext> create(HTMLCanvasElement*, const CanvasContextCreationAttributes&);
     ~WebGL2RenderingContext() override;
 
     unsigned version() const override { return 2; }
     String contextName() const override { return "WebGL2RenderingContext"; }
     void registerContextExtensions() override;
 
     void trace(Visitor*) override;
 
 protected:
     WebGL2RenderingContext(HTMLCanvasElement* passedCanvas, PassOwnPtr<blink::WebGraphicsContext3D>, const WebGLContextAttributes& requestedAttributes);
 
-    RefPtr<WebGLDebugRendererInfo> m_webglDebugRendererInfo;
-    RefPtr<WebGLDebugShaders> m_webglDebugShaders;
+    RefPtrWillBeMember<WebGLDebugRendererInfo> m_webglDebugRendererInfo;
+    RefPtrWillBeMember<WebGLDebugShaders> m_webglDebugShaders;
 };
 
 DEFINE_TYPE_CASTS(WebGL2RenderingContext, CanvasRenderingContext, context,
     context->is3d() && WebGLRenderingContextBase::getWebGLVersion(context) == 2,
     context.is3d() && WebGLRenderingContextBase::getWebGLVersion(&context) == 2);
 
 } // namespace blink
 
 #endif