Android: Don't destroy LayerTreeHost when Surface goes away

ui/android/resources/ui_resource_android.cc

 // 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.
 
 #include "ui/android/resources/ui_resource_android.h"
 
 #include "base/logging.h"
 #include "ui/android/resources/ui_resource_provider.h"
 
 namespace ui {
@@ skipping 20 matching lines @@
 
 cc::UIResourceId UIResourceAndroid::id() {
   if (id_)
     return id_;
   if (!provider_ || bitmap_.empty())
     return 0;
   id_ = provider_->CreateUIResource(this);
   return id_;
 }
 
-void UIResourceAndroid::UIResourceIsInvalid() {
-  id_ = 0;
-}
-
 UIResourceAndroid::UIResourceAndroid(ui::UIResourceProvider* provider,
                                      const SkBitmap& skbitmap)
     : provider_(provider), bitmap_(skbitmap), id_(0) {
 }
 
 }  // namespace ui