Add window property for restore bounds when virtual keyboard is enabled.

ash/mus/bridge/wm_window_mus.cc

Index: ash/mus/bridge/wm_window_mus.cc
diff --git a/ash/mus/bridge/wm_window_mus.cc b/ash/mus/bridge/wm_window_mus.cc
index d779cf4ec90edc4f0d88f0c55e6fc8ef80a5131a..34e5d367fb3d6f0445940843e7b5b0555d82adb0 100644
--- a/ash/mus/bridge/wm_window_mus.cc
+++ b/ash/mus/bridge/wm_window_mus.cc
@@ -367,6 +367,11 @@ void WmWindowMus::SetIntProperty(WmWindowProperty key, int value) {
   NOTREACHED();
 }
 
+gfx::Rect* WmWindowMus::GetRectProperty(WmWindowProperty key) {
+  NOTIMPLEMENTED();  // TODO: Add support; see crbug.com/638416
+  return nullptr;
+}
+
 ShelfItemDetails* WmWindowMus::GetShelfItemDetails() {
   NOTIMPLEMENTED();  // TODO: Add support; see crbug.com/634150
   return nullptr;