Android: Don't destroy LayerTreeHost when Surface goes away

ui/android/resources/ui_resource_provider.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_provider.h"
 
 #include "cc/resources/ui_resource_client.h"
 #include "cc/trees/layer_tree_host.h"
 #include "ui/android/resources/ui_resource_client_android.h"
 
 namespace ui {
 
-UIResourceProvider::UIResourceProvider()
-    : host_(NULL), supports_etc1_npot_(false) {
+UIResourceProvider::UIResourceProvider(cc::LayerTreeHost* host)
+    : host_(host), supports_etc1_npot_(false) {
 }
 
 UIResourceProvider::~UIResourceProvider() {
-  SetLayerTreeHost(NULL);
+  OnUIResourcesEvicted();
 }
 
-void UIResourceProvider::SetLayerTreeHost(cc::LayerTreeHost* host) {
-  if (host_ == host)
-    return;
-  host_ = host;
-  UIResourcesAreInvalid();
-}
-
-void UIResourceProvider::UIResourcesAreInvalid() {
-  UIResourceClientMap client_map;
-  client_map.swap(ui_resource_client_map_);
+void UIResourceProvider::OnUIResourcesEvicted() {
+  // OnWasEvicted() might cause DeleteUIResource() to get called.
+  UIResourceClientMap client_map(ui_resource_client_map_);
   for (UIResourceClientMap::iterator iter = client_map.begin();
        iter != client_map.end(); iter++) {
-    iter->second->UIResourceIsInvalid();
+    iter->second->OnWasEvicted();
   }
 }
 
 cc::UIResourceId UIResourceProvider::CreateUIResource(
     ui::UIResourceClientAndroid* client) {
-  if (!host_)
-    return 0;
   cc::UIResourceId id = host_->CreateUIResource(client);
   DCHECK(ui_resource_client_map_.find(id) == ui_resource_client_map_.end());
 
   ui_resource_client_map_[id] = client;
   return id;
 }
 
 void UIResourceProvider::DeleteUIResource(cc::UIResourceId ui_resource_id) {
   UIResourceClientMap::iterator iter =
       ui_resource_client_map_.find(ui_resource_id);
   DCHECK(iter != ui_resource_client_map_.end());
 
   ui_resource_client_map_.erase(iter);
-
-  if (!host_)
-    return;
   host_->DeleteUIResource(ui_resource_id);
 }
 
 bool UIResourceProvider::SupportsETC1NonPowerOfTwo() const {
   return supports_etc1_npot_;
 }
 
 }  // namespace ui