Reify view ownership as a message pipe.

services/ui/launcher/launcher_view_tree.cc

 // Copyright 2015 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 "services/ui/launcher/launcher_view_tree.h"
 
 #include "base/bind.h"
 #include "mojo/public/cpp/application/connect.h"
 #include "mojo/services/gfx/composition/cpp/formatting.h"
 #include "mojo/services/ui/views/cpp/formatting.h"
@@ skipping 30 matching lines @@
       base::Bind(&LauncherViewTree::OnSceneRegistered, base::Unretained(this)));
   mojo::gfx::composition::SceneListenerPtr scene_listener;
   scene_listener_binding_.Bind(mojo::GetProxy(&scene_listener));
   scene_->SetListener(scene_listener.Pass());
   scene_.set_connection_error_handler(base::Bind(
       &LauncherViewTree::OnSceneConnectionError, base::Unretained(this)));
 
   // Register the view tree.
   mojo::ui::ViewTreePtr view_tree;
   view_tree_binding_.Bind(mojo::GetProxy(&view_tree));
-  view_manager_->RegisterViewTree(
-      view_tree.Pass(), mojo::GetProxy(&view_tree_host_), "Launcher",
-      base::Bind(&LauncherViewTree::OnViewTreeRegistered,
-                 base::Unretained(this)));
+  view_manager_->RegisterViewTree(view_tree.Pass(),
+                                  mojo::GetProxy(&view_tree_host_), "Launcher");
   view_tree_host_.set_connection_error_handler(base::Bind(
       &LauncherViewTree::OnViewTreeConnectionError, base::Unretained(this)));
 
   // Get view tree services.
   mojo::ServiceProviderPtr view_tree_service_provider;
   view_tree_host_->GetServiceProvider(
       mojo::GetProxy(&view_tree_service_provider));
   mojo::ConnectToService<mojo::ui::InputDispatcher>(
       view_tree_service_provider.get(), &input_dispatcher_);
   input_dispatcher_.set_connection_error_handler(
       base::Bind(&LauncherViewTree::OnInputDispatcherConnectionError,
                  base::Unretained(this)));
 }
 
 LauncherViewTree::~LauncherViewTree() {}
 
-void LauncherViewTree::SetRoot(mojo::ui::ViewTokenPtr token) {
-  root_ = token.Pass();
-  if (root_)
-    view_tree_host_->SetRoot(++root_key_, root_.Clone());
-  else
-    view_tree_host_->ResetRoot();
+void LauncherViewTree::SetRoot(mojo::ui::ViewOwnerPtr owner) {
+  if (owner) {
+    view_tree_host_->SetRoot(++root_key_, owner.Pass());
+    root_was_set_ = true;
+  } else {
+    view_tree_host_->ResetRoot(nullptr);
+    root_was_set_ = false;
+  }
   root_layout_info_.reset();
 }
 
 void LauncherViewTree::SetViewportMetrics(
     mojo::ViewportMetricsPtr viewport_metrics) {
   viewport_metrics_ = viewport_metrics.Pass();
   view_tree_host_->RequestLayout();
   SetRootScene();
 }
 
@@ skipping 24 matching lines @@
   input_dispatcher_.reset();
 }
 
 void LauncherViewTree::OnSceneRegistered(
     mojo::gfx::composition::SceneTokenPtr scene_token) {
   DVLOG(1) << "OnSceneRegistered: scene_token=" << scene_token;
   scene_token_ = scene_token.Pass();
   SetRootScene();
 }
 
-void LauncherViewTree::OnViewTreeRegistered(
-    mojo::ui::ViewTreeTokenPtr view_tree_token) {
-  DVLOG(1) << "OnViewTreeRegistered: view_tree_token=" << view_tree_token;
-}
-
 void LauncherViewTree::OnResourceUnavailable(
     uint32_t resource_id,
     const OnResourceUnavailableCallback& callback) {
   LOG(ERROR) << "Resource lost: resource_id=" << resource_id;
 }
 
 void LauncherViewTree::OnLayout(const OnLayoutCallback& callback) {
   LayoutRoot();
   callback.Run();
 }
 
 void LauncherViewTree::OnRootUnavailable(
     uint32_t root_key,
     const OnRootUnavailableCallback& callback) {
   if (root_key_ == root_key) {
     LOG(ERROR) << "Root view terminated unexpectedly.";
     Shutdown();
   }
   callback.Run();
 }
 
 void LauncherViewTree::LayoutRoot() {
-  if (!root_)
+  if (!root_was_set_)
     return;
 
   auto params = mojo::ui::ViewLayoutParams::New();
   params->constraints = mojo::ui::BoxConstraints::New();
   params->constraints->min_width = viewport_metrics_->size->width;
   params->constraints->max_width = viewport_metrics_->size->width;
   params->constraints->min_height = viewport_metrics_->size->height;
   params->constraints->max_height = viewport_metrics_->size->height;
   params->device_pixel_ratio = viewport_metrics_->device_pixel_ratio;
   view_tree_host_->LayoutRoot(
@@ skipping 73 matching lines @@
 
   scene_->Update(update.Pass());
   scene_->Publish(metadata.Pass());
 }
 
 void LauncherViewTree::Shutdown() {
   shutdown_callback_.Run();
 }
 
 }  // namespace launcher