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

content/browser/android/content_view_core_impl.cc

 // Copyright 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.
 
 #include "content/browser/android/content_view_core_impl.h"
 
 #include "base/android/jni_android.h"
 #include "base/android/jni_array.h"
 #include "base/android/jni_string.h"
 #include "base/android/scoped_java_ref.h"
@@ skipping 319 matching lines @@
     if (!obj.is_null()) {
       Java_ContentViewCore_onRenderProcessChange(env, obj.obj());
     }
   }
 
   SetFocusInternal(HasFocus());
   SetAccessibilityEnabledInternal(accessibility_enabled_);
 }
 
 RenderWidgetHostViewAndroid*
-    ContentViewCoreImpl::GetRenderWidgetHostViewAndroid() {
+    ContentViewCoreImpl::GetRenderWidgetHostViewAndroid() const {
   RenderWidgetHostView* rwhv = NULL;
   if (web_contents_) {
     rwhv = web_contents_->GetRenderWidgetHostView();
     if (web_contents_->ShowingInterstitialPage()) {
       rwhv = static_cast<InterstitialPageImpl*>(
           web_contents_->GetInterstitialPage())->
               GetRenderViewHost()->GetView();
     }
   }
   return static_cast<RenderWidgetHostViewAndroid*>(rwhv);
@@ skipping 440 matching lines @@
 }
 
 ui::ViewAndroid* ContentViewCoreImpl::GetViewAndroid() const {
   return view_android_;
 }
 
 ui::WindowAndroid* ContentViewCoreImpl::GetWindowAndroid() const {
   return window_android_;
 }
 
-scoped_refptr<cc::Layer> ContentViewCoreImpl::GetLayer() const {
-  return root_layer_.get();
+const scoped_refptr<cc::Layer>& ContentViewCoreImpl::GetLayer() const {
+  return root_layer_;
 }
 
 // ----------------------------------------------------------------------------
 // Methods called from Java via JNI
 // ----------------------------------------------------------------------------
 
 void ContentViewCoreImpl::SelectPopupMenuItems(JNIEnv* env,
                                                jobject obj,
                                                jlong selectPopupSourceFrame,
                                                jintArray indices) {
@@ skipping 520 matching lines @@
       reinterpret_cast<ui::WindowAndroid*>(window_android),
       retained_objects_set);
   return reinterpret_cast<intptr_t>(view);
 }
 
 bool RegisterContentViewCore(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 }  // namespace content