ash/mash: Add a mus-client that sets up ash to provide the system ui for mash.

ash/host/ash_window_tree_host.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 "ash/host/ash_window_tree_host.h"
 
 #include "ash/host/ash_window_tree_host_init_params.h"
 #include "ash/host/ash_window_tree_host_unified.h"
 #include "ui/aura/client/screen_position_client.h"
 #include "ui/aura/window_tree_host.h"
 #include "ui/events/event.h"
 #include "ui/gfx/geometry/rect.h"
 
 #if defined(USE_OZONE)
 #include "ash/host/ash_window_tree_host_platform.h"
 #elif defined(USE_X11)
 #include "ash/host/ash_window_tree_host_x11.h"
 #elif defined(OS_WIN)
 #include "ash/host/ash_window_tree_host_win.h"
 #endif
 
 namespace ash {
 
+namespace {
+
+AshWindowTreeHost::Factory creation_factory;
+
+}  // namespace
+
 AshWindowTreeHost::AshWindowTreeHost() : input_method_handler_(nullptr) {
 }
 
 void AshWindowTreeHost::TranslateLocatedEvent(ui::LocatedEvent* event) {
   if (event->IsTouchEvent())
     return;
 
   aura::WindowTreeHost* wth = AsWindowTreeHost();
   aura::Window* root_window = wth->window();
   aura::client::ScreenPositionClient* screen_position_client =
       aura::client::GetScreenPositionClient(root_window);
   gfx::Rect local(wth->GetBounds().size());
   local.Inset(GetHostInsets());
 
   if (screen_position_client && !local.Contains(event->location())) {
     gfx::Point location(event->location());
     // In order to get the correct point in screen coordinates
     // during passive grab, we first need to find on which host window
     // the mouse is on, and find out the screen coordinates on that
     // host window, then convert it back to this host window's coordinate.
     screen_position_client->ConvertHostPointToScreen(root_window, &location);
     screen_position_client->ConvertPointFromScreen(root_window, &location);
     wth->ConvertPointToHost(&location);
     event->set_location(location);
     event->set_root_location(location);
   }
 }
 
+// static
 AshWindowTreeHost* AshWindowTreeHost::Create(
     const AshWindowTreeHostInitParams& init_params) {
+  if (!creation_factory.is_null())
+    return creation_factory.Run(init_params);
+
   if (init_params.offscreen)
     return new AshWindowTreeHostUnified(init_params.initial_bounds);
 #if defined(USE_OZONE)
   return new AshWindowTreeHostPlatform(init_params.initial_bounds);
 #elif defined(USE_X11)
   return new AshWindowTreeHostX11(init_params.initial_bounds);
 #elif defined(OS_WIN)
   return new AshWindowTreeHostWin(init_params.initial_bounds);
 #else
 #error Unsupported platform.
 #endif
 }
 
+// static
+void AshWindowTreeHost::SetFactory(const Factory& factory) {
+  creation_factory = factory;
+}
+
 }  // namespace ash