Mus Demo: Demonstrate external window mode

services/ui/demo/window_tree_data.h

Index: services/ui/demo/window_tree_data.h
diff --git a/services/ui/demo/window_tree_data.h b/services/ui/demo/window_tree_data.h
index 0e1bcbd0806f8cc96f1feb5cdaf4c26a18b5d571..a80856ef71c14978389e2b6a44563a7eb3a6115a 100644
--- a/services/ui/demo/window_tree_data.h
+++ b/services/ui/demo/window_tree_data.h
@@ -7,6 +7,7 @@
 
 #include "base/memory/ptr_util.h"
 #include "base/timer/timer.h"
+#include "services/ui/public/interfaces/window_tree_host.mojom.h"
 
 namespace aura {
 class Window;
@@ -23,6 +24,9 @@ namespace demo {
 class WindowTreeData {
  public:
   explicit WindowTreeData(int square_size);

[kylechar, 2017/02/21 15:15:11]

What is the difference between the two constructors? Can you add comments.

[fwang, 2017/02/21 17:30:19]

The new one is only used in external mode. I've moved it to
WindowTreeDataExternal so that it is clearer.

+  explicit WindowTreeData(mojom::WindowTreeHostFactory* factory,

[kylechar, 2017/02/21 15:15:11]

Only constructor with a single parameter should be explicit.

[fwang, 2017/02/21 17:30:19]

Done.

+                          mojom::WindowTreeClientPtr tree_client,
+                          int square_size);
   ~WindowTreeData();
 
   // Initializes the window tree host and start drawing frames.
@@ -39,6 +43,10 @@ class WindowTreeData {
   // The Window tree host corresponding to this data.
   std::unique_ptr<aura::WindowTreeHostMus> window_tree_host_;
 
+  // When the WindowTreeData is created with WindowTreeHostFactory, this holds
+  // the Mojo pointer to the window tree host.
+  mojom::WindowTreeHostPtr host_;

[kylechar, 2017/02/21 15:15:11]

Is this only needed for external mode? Can we somehow have only shared code in
WindowTreeData?

[fwang, 2017/02/21 17:30:19]

Yes. All these data will be moved to a WindowTreeDataExternal.

+
   // Destroys itself when the window gets destroyed.
   aura_extra::ImageWindowDelegate* window_delegate_ = nullptr;