Changes how window is updated when display changes in mash

ash/mus/window_manager.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 "ash/mus/window_manager.h"
 
 #include <stdint.h>
 
 #include <utility>
 
@@ skipping 467 matching lines @@
     if (root_window_controller_ptr->GetHost() == window_tree_host) {
       const bool in_shutdown = false;
       DestroyRootWindowController(root_window_controller_ptr.get(),
                                   in_shutdown);
       break;
     }
   }
 }
 
 void WindowManager::OnWmDisplayModified(const display::Display& display) {
-  screen_->display_list().UpdateDisplay(display);
+  // Ash relies on the Display being updated, then the WindowTreeHost's window,
+  // and finally DisplayObservers.
+  std::unique_ptr<display::DisplayListObserverLock> display_lock =
+      screen_->display_list().SuspendObserverUpdates();
+  const bool is_primary =
+      screen_->display_list().FindDisplayById(display.id()) ==
+      screen_->display_list().GetPrimaryDisplayIterator();
+  uint32_t display_changed_values = screen_->display_list().UpdateDisplay(
+      display, is_primary ? display::DisplayList::Type::PRIMARY
+                          : display::DisplayList::Type::NOT_PRIMARY);
+  RootWindowController* root_window_controller =
+      WmShellMus::Get()->GetRootWindowControllerWithDisplayId(display.id());
+  DCHECK(root_window_controller);
+  root_window_controller->GetRootWindow()->GetHost()->SetBoundsInPixels(
+      display.bounds());
+  display_lock.reset();
+  for (display::DisplayObserver& observer :
+       *(screen_->display_list().observers())) {
+    observer.OnDisplayMetricsChanged(display, display_changed_values);
+  }

[James Cook, 2017/03/30 15:34:34]

optional: line wrapping in this function might be better with "using
display::DisplayList" and/or putting screen_->display_list() in a local.

[sky, 2017/03/30 19:04:24]

I went with making a local for screen_->display_list().

 }
 
 void WindowManager::OnWmPerformMoveLoop(
     aura::Window* window,
     ui::mojom::MoveLoopSource source,
     const gfx::Point& cursor_location,
     const base::Callback<void(bool)>& on_done) {
   WmWindow* child_window = WmWindow::Get(window);
   MoveEventHandler* handler = MoveEventHandler::GetForWindow(child_window);
   if (!handler) {
@@ skipping 41 matching lines @@
 bool WindowManager::IsWindowActive(aura::Window* window) {
   return Shell::GetInstance()->activation_client()->GetActiveWindow() == window;
 }
 
 void WindowManager::OnWmDeactivateWindow(aura::Window* window) {
   Shell::GetInstance()->activation_client()->DeactivateWindow(window);
 }
 
 }  // namespace mus
 }  // namespace ash