Add OnDisplayMetricsChanged in DisplayObserver.

ash/wm/maximize_mode/maximize_mode_window_manager.cc

Index: ash/wm/maximize_mode/maximize_mode_window_manager.cc
diff --git a/ash/wm/maximize_mode/maximize_mode_window_manager.cc b/ash/wm/maximize_mode/maximize_mode_window_manager.cc
index 1b9f9dbadb4b8d20950c9b9d46af965a4f8013b9..36a641885ff7a7af805c08a8ffa7a3246a0a1938 100644
--- a/ash/wm/maximize_mode/maximize_mode_window_manager.cc
+++ b/ash/wm/maximize_mode/maximize_mode_window_manager.cc
@@ -108,11 +108,6 @@ void MaximizeModeWindowManager::OnWindowBoundsChanged(
   }
 }
 
-void MaximizeModeWindowManager::OnDisplayBoundsChanged(
-    const gfx::Display& display) {
-  // Nothing to do here.
-}
-
 void MaximizeModeWindowManager::OnDisplayAdded(const gfx::Display& display) {
   DisplayConfigurationChanged();
 }
@@ -121,6 +116,11 @@ void MaximizeModeWindowManager::OnDisplayRemoved(const gfx::Display& display) {
   DisplayConfigurationChanged();
 }
 
+void MaximizeModeWindowManager::OnDisplayMetricsChanged(
+    const gfx::Display&, DisplayObserver::MetricsType) {
+  // Nothing to do here.
+}
+
 MaximizeModeWindowManager::MaximizeModeWindowManager()
       : backdrops_hidden_(false) {
   // The overview mode needs to be ended before the maximize mode is started. To