Allow parallel creation of windows

services/ui/demo/mus_demo_external.cc

Index: services/ui/demo/mus_demo_external.cc
diff --git a/services/ui/demo/mus_demo_external.cc b/services/ui/demo/mus_demo_external.cc
index f76c0a8dedbb0952bb9b9b23f555755a2acbb644..25ecc72887ed7d2994f32df56efb3c0327e5f732 100644
--- a/services/ui/demo/mus_demo_external.cc
+++ b/services/ui/demo/mus_demo_external.cc
@@ -66,29 +66,19 @@ void MusDemoExternal::OnStartImpl() {
   // aura::GetDeviceScaleFactorFromDisplay().
   AddPrimaryDisplay(display::Display(0));
 
-  // TODO(tonikitoo,fwang): New windows can be launched without need to wait
-  // the respective ::OnEmbed call of the previous instance.
-  OpenNewWindow();
+  for (size_t i = 0; i < number_of_windows_; ++i)
+    OpenNewWindow(i);
 }
 
-void MusDemoExternal::OpenNewWindow() {
+void MusDemoExternal::OpenNewWindow(size_t window_count) {

[fwang, 2017/03/16 08:59:49]

window_index

[msisov(use msisov igalia.com), 2017/03/16 09:21:32]

Done.

   AppendWindowTreeData(base::MakeUnique<WindowTreeDataExternal>(
-      window_tree_client(),
-      GetSquareSizeForWindow(initialized_windows_count_)));
+      window_tree_client(), GetSquareSizeForWindow(window_count)));

[fwang, 2017/03/16 08:59:49]

window_index

[msisov(use msisov igalia.com), 2017/03/16 09:21:32]

Done.

 }
 
-void MusDemoExternal::OnEmbed(
-    std::unique_ptr<aura::WindowTreeHostMus> window_tree_host) {
-  DCHECK(!window_tree_host);
-
-  // TODO: Clean up WindowTreeClientDelegate::OnEmbed API so that it passes
-  // no ownership of WindowTreeHostMus instance.
-  InitWindowTreeData(nullptr);
-  initialized_windows_count_++;
-
-  // Open the next window until the requested number of windows is reached.
-  if (initialized_windows_count_ < number_of_windows_)
-    OpenNewWindow();
+void MusDemoExternal::OnEmbedRootReady(
+    aura::WindowTreeHostMus* window_tree_host) {
+  DCHECK(window_tree_host);
+  InitWindowTreeDataExternal(window_tree_host);

[fwang, 2017/03/16 08:59:48]

I seems you can get rid of InitWindowTreeDataExternal and just implement the
init in the body of OnEmbedRootReady.

[msisov(use msisov igalia.com), 2017/03/16 09:21:32]

Done.

 }
 
 void MusDemoExternal::OnEmbedRootDestroyed(