[Android] Add a native pull-to-refresh overscroll effect

content/public/browser/android/content_view_core.h

 // Copyright (c) 2012 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 CONTENT_PUBLIC_BROWSER_ANDROID_CONTENT_VIEW_CORE_H_
 #define CONTENT_PUBLIC_BROWSER_ANDROID_CONTENT_VIEW_CORE_H_
 
 #include <jni.h>
 
 #include "base/android/scoped_java_ref.h"
@@ skipping 29 matching lines @@
 class CONTENT_EXPORT ContentViewCore {
  public:
   // Returns the existing ContentViewCore for |web_contents|, or NULL.
   static ContentViewCore* FromWebContents(WebContents* web_contents);
   static ContentViewCore* GetNativeContentViewCore(JNIEnv* env, jobject obj);
 
   virtual WebContents* GetWebContents() const = 0;
   virtual base::android::ScopedJavaLocalRef<jobject> GetJavaObject() = 0;
   virtual ui::ViewAndroid* GetViewAndroid() const = 0;
   virtual ui::WindowAndroid* GetWindowAndroid() const = 0;
-  virtual scoped_refptr<cc::Layer> GetLayer() const = 0;
+  virtual const scoped_refptr<cc::Layer>& GetLayer() const = 0;
   virtual void ShowPastePopup(int x, int y) = 0;
 
   // Request a scaled content readback. The result is passed through the
   // callback. The boolean parameter indicates whether the readback was a
   // success or not. The content is passed through the SkBitmap parameter.
   virtual void GetScaledContentBitmap(
       float scale,
       SkColorType color_type,
       gfx::Rect src_rect,
       const base::Callback<void(bool, const SkBitmap&)>& result_callback) = 0;
@@ skipping 13 matching lines @@
                                 int start_offset,
                                 int end_offset)>& callback) = 0;
 
  protected:
   virtual ~ContentViewCore() {};
 };
 
 };  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_ANDROID_CONTENT_VIEW_CORE_H_