[Oilpan] Migrate classes under module/webgl onto oilpan heap

Source/modules/webgl/EXTsRGB.h

 // Copyright 2014 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 EXTsRGB_h
 #define EXTsRGB_h
 
 #include "modules/webgl/WebGLExtension.h"
-#include "wtf/PassRefPtr.h"
 
 namespace blink {
 
 class EXTsRGB final : public WebGLExtension {
     DEFINE_WRAPPERTYPEINFO();
 public:
-    static PassRefPtrWillBeRawPtr<EXTsRGB> create(WebGLRenderingContextBase*);
+    static EXTsRGB* create(WebGLRenderingContextBase*);
     static bool supported(WebGLRenderingContextBase*);
     static const char* extensionName();
 
     ~EXTsRGB() override;
     WebGLExtensionName name() const override;
 
 private:
     explicit EXTsRGB(WebGLRenderingContextBase*);
 };
 
 } // namespace blink
 
 #endif // EXTsRGB_h