Add virtualKeyboardPrivate.onKeyboardClosed API.

ash/common/wm/system_modal_container_layout_manager.cc

Index: ash/common/wm/system_modal_container_layout_manager.cc
diff --git a/ash/common/wm/system_modal_container_layout_manager.cc b/ash/common/wm/system_modal_container_layout_manager.cc
index 46aa21f64721c6c0611b2ff147f7afacbba7689a..4185abf49d47879c1da3b2e1b42f03f23e5157c8 100644
--- a/ash/common/wm/system_modal_container_layout_manager.cc
+++ b/ash/common/wm/system_modal_container_layout_manager.cc
@@ -44,7 +44,10 @@ SystemModalContainerLayoutManager::SystemModalContainerLayoutManager(
     WmWindow* container)
     : container_(container) {}
 
-SystemModalContainerLayoutManager::~SystemModalContainerLayoutManager() {}
+SystemModalContainerLayoutManager::~SystemModalContainerLayoutManager() {
+  if (keyboard::KeyboardController::GetInstance())
+    keyboard::KeyboardController::GetInstance()->RemoveObserver(this);
+}
 
 ////////////////////////////////////////////////////////////////////////////////
 // SystemModalContainerLayoutManager, WmLayoutManager implementation:
@@ -130,6 +133,8 @@ void SystemModalContainerLayoutManager::OnKeyboardBoundsChanging(
   PositionDialogsAfterWorkAreaResize();
 }
 
+void SystemModalContainerLayoutManager::OnKeyboardClosed() {}
+
 bool SystemModalContainerLayoutManager::IsPartOfActiveModalWindow(
     WmWindow* window) {
   return modal_window() &&