Add flag to launch two displays for mus+ash.

services/ui/ws/display.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/ws/display.h"
 
 #include <set>
 #include <utility>
 #include <vector>
 
@@ skipping 297 matching lines @@
 void Display::OnDisplayClosed() {
   display_manager()->DestroyDisplay(this);
 }
 
 void Display::OnViewportMetricsChanged(const ViewportMetrics& old_metrics,
                                        const ViewportMetrics& new_metrics) {
   if (!root_) {
     root_.reset(window_server_->CreateServerWindow(
         display_manager()->GetAndAdvanceNextRootId(),
         ServerWindow::Properties()));
-    root_->SetBounds(gfx::Rect(new_metrics.size_in_pixels));
+    root_->SetBounds(new_metrics.bounds);
     root_->SetVisible(true);
     focus_controller_.reset(new FocusController(this, root_.get()));
     focus_controller_->AddObserver(this);
     InitWindowManagerDisplayRootsIfNecessary();
   } else {
-    root_->SetBounds(gfx::Rect(new_metrics.size_in_pixels));
+    root_->SetBounds(new_metrics.bounds);
     const gfx::Rect wm_bounds(root_->bounds().size());
     for (auto& pair : window_manager_display_root_map_)
       pair.second->root()->SetBounds(wm_bounds);
   }
   display_manager()->OnDisplayUpdate(this);
 }
 
 void Display::OnCompositorFrameDrawn() {
   std::set<ServerWindow*> windows;
   windows.swap(windows_needing_frame_destruction_);
@@ skipping 89 matching lines @@
 }
 
 void Display::OnWindowManagerWindowTreeFactoryReady(
     WindowManagerWindowTreeFactory* factory) {
   if (!binding_)
     CreateWindowManagerDisplayRootFromFactory(factory);
 }
 
 }  // namespace ws
 }  // namespace ui