Add OnDisplayMetricsChanged in DisplayObserver.

ash/wm/overview/window_overview.cc

Index: ash/wm/overview/window_overview.cc
diff --git a/ash/wm/overview/window_overview.cc b/ash/wm/overview/window_overview.cc
index f84d633f57a5b704e3bddd8a8b2a135c67b254c3..a48db09b0db7cb3d1d5ff21b86710b09fa52940c 100644
--- a/ash/wm/overview/window_overview.cc
+++ b/ash/wm/overview/window_overview.cc
@@ -298,16 +298,18 @@ void WindowOverview::OnTouchEvent(ui::TouchEvent* event) {
   window_selector_->SelectWindow(target);
 }
 
-void WindowOverview::OnDisplayBoundsChanged(const gfx::Display& display) {
-  PositionWindows(/* animate */ false);
-}
-
 void WindowOverview::OnDisplayAdded(const gfx::Display& display) {
 }
 
 void WindowOverview::OnDisplayRemoved(const gfx::Display& display) {
 }
 
+void WindowOverview::OnDisplayMetricsChanged(
+    const gfx::Display& display,
+    gfx::DisplayObserver::DisplayMetrics metrics) {
+  PositionWindows(/* animate */ false);
+}
+
 aura::Window* WindowOverview::GetEventTarget(ui::LocatedEvent* event) {
   aura::Window* target = static_cast<aura::Window*>(event->target());
   // If the target window doesn't actually contain the event location (i.e.