Handle modified displays in mustash.

ash/mus/window_manager.cc

Index: ash/mus/window_manager.cc
diff --git a/ash/mus/window_manager.cc b/ash/mus/window_manager.cc
index b72aa50567abffd463384d88d6714b256d5a3a2e..f02e2c2ed427f6ed0482cf31c69d179fe953e9ee 100644
--- a/ash/mus/window_manager.cc
+++ b/ash/mus/window_manager.cc
@@ -24,6 +24,7 @@
 #include "ash/mus/window_manager_observer.h"
 #include "ash/public/cpp/shell_window_ids.h"
 #include "base/memory/ptr_util.h"
+#include "services/service_manager/public/cpp/connector.h"
 #include "services/ui/common/event_matcher_util.h"
 #include "services/ui/common/types.h"
 #include "services/ui/public/cpp/property_type_converters.h"
@@ -54,6 +55,10 @@ void WindowManager::Init(
   DCHECK(!window_tree_client_);
   window_tree_client_ = std::move(window_tree_client);
 
+  // |connector_| will be null in some tests.
+  if (connector_)
+    connector_->ConnectToInterface("service:ui", &display_controller_);
+
   screen_ = base::MakeUnique<display::ScreenBase>();
 
   pointer_watcher_event_router_.reset(
@@ -136,6 +141,10 @@ void WindowManager::RemoveObserver(WindowManagerObserver* observer) {
   observers_.RemoveObserver(observer);
 }
 
+display::mojom::DisplayController* WindowManager::GetDisplayController() {
+  return display_controller_ ? display_controller_.get() : nullptr;
+}
+
 RootWindowController* WindowManager::CreateRootWindowController(
     ui::Window* window,
     const display::Display& display) {
@@ -333,6 +342,18 @@ void WindowManager::OnWmDisplayRemoved(ui::Window* window) {
   DestroyRootWindowController(iter->get());
 }
 
+void WindowManager::OnWmDisplayModified(const display::Display& display) {
+  for (auto& controller : root_window_controllers_) {
+    if (controller->display().id() == display.id()) {
+      controller->SetDisplay(display);
+      // The root window will be resized by the window server.
+      return;
+    }
+  }
+
+  NOTREACHED();
+}
+
 void WindowManager::OnWmPerformMoveLoop(
     ui::Window* window,
     ui::mojom::MoveLoopSource source,