android: content::UIResourceProvider and content::UIResourceClientAndroid

content/browser/android/ui_resource_provider_impl.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 "content/browser/android/ui_resource_provider_impl.h"
+
+#include "cc/resources/ui_resource_client.h"
+#include "cc/trees/layer_tree_host.h"
+#include "content/public/browser/android/ui_resource_client_android.h"
+
+namespace content {
+
+UIResourceProviderImpl::UIResourceProviderImpl() : host_(NULL) {
+}
+
+UIResourceProviderImpl::~UIResourceProviderImpl() {
+  SetLayerTreeHost(NULL);
+}
+
+void UIResourceProviderImpl::SetLayerTreeHost(cc::LayerTreeHost* host) {
+  if (host_ == host)
+    return;
+  host_ = host;
+  UIResourcesAreInvalid();
+}
+
+void UIResourceProviderImpl::UIResourcesAreInvalid() {
+  UIResourceClientMap client_map = ui_resource_client_map_;
+  ui_resource_client_map_.clear();
+  for (UIResourceClientMap::iterator iter = client_map.begin();
+       iter != client_map.end();
+       iter++) {
+    iter->second->UIResourceIsInvalid();
+  }
+}
+
+cc::UIResourceId UIResourceProviderImpl::CreateUIResource(
+    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 UIResourceProviderImpl::DeleteUIResource(cc::UIResourceId ui_resource_id) {
+  UIResourceClientMap::iterator iter =
+      ui_resource_client_map_.find(ui_resource_id);
+  if (iter == ui_resource_client_map_.end())

[no sievers, 2014/06/11 23:00:09]

This is a bit risky: If resources become invalid but the client still tries to
delete an old resource (I assume that's why you allow returning here), this
resource id might as well be a valid id for a new resource that was created in
the meantime. Then we would not return here, but delete it below.

Should we DCHECK() here and say that UIResourcesAreInvalid() means the user
should not call DeleteUIResource() for any ids returned from Create() calls
before that? (since we clear the map anyways)

[powei, 2014/06/13 00:02:10]

Done.  Put this in a dcheck and added a comment in the client interface.

+    return;
+
+  ui_resource_client_map_.erase(iter);
+
+  if (!host_)
+    return;
+  host_->DeleteUIResource(ui_resource_id);
+}
+
+}  // namespace content