Add support for multiple roots to the client lib.

mojo/examples/embedded_app/embedded_app.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 "base/basictypes.h"
+#include "base/bind.h"
 #include "mojo/public/cpp/application/application.h"
 #include "mojo/services/public/cpp/view_manager/view.h"
 #include "mojo/services/public/cpp/view_manager/view_manager.h"
 #include "mojo/services/public/cpp/view_manager/view_tree_node.h"
 
 namespace mojo {
 namespace examples {
 
 class EmbeddedApp : public Application {
  public:
-  EmbeddedApp() {}
+  EmbeddedApp() : view_manager_(NULL) {}
   virtual ~EmbeddedApp() {}
 
  private:
   // Overridden from Application:
   virtual void Initialize() MOJO_OVERRIDE {
-    view_manager_ = view_manager::ViewManager::CreateBlocking(this);
-    view_manager::View* view = view_manager::View::Create(view_manager_);
-    view_manager_->tree()->SetActiveView(view);
-    view->SetColor(SK_ColorYELLOW);
+    view_manager::ViewManager::Create(this,
+        base::Bind(&EmbeddedApp::OnRootAdded, base::Unretained(this)));
+  }
+
+  void OnRootAdded(view_manager::ViewManager* view_manager) {
+    if (!view_manager_)
+      view_manager_ = view_manager;
+    DCHECK_EQ(view_manager_, view_manager);
+
+    if (view_manager_->roots().size() == 1) {
+      view_manager::View* view = view_manager::View::Create(view_manager_);
+      view_manager_->roots().front()->SetActiveView(view);
+      view->SetColor(SK_ColorYELLOW);
+    } else {
+      view_manager::View* view = view_manager::View::Create(view_manager_);
+      view_manager_->roots().back()->SetActiveView(view);
+      view->SetColor(SK_ColorRED);
+    }
   }
 
   view_manager::ViewManager* view_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(EmbeddedApp);
 };
 
 }  // namespace examples
 
 // static
 Application* Application::Create() {
   return new examples::EmbeddedApp;
 }
 
 }  // namespace mojo