ash: Start/stop observing KeyboardController via ShellObserver

ash/common/wm/dock/docked_window_layout_manager.h

Index: ash/common/wm/dock/docked_window_layout_manager.h
diff --git a/ash/common/wm/dock/docked_window_layout_manager.h b/ash/common/wm/dock/docked_window_layout_manager.h
index f363890758ddfc0d1f38410cdbc389abd495f13c..f51e73b06d1fc722b3d7353a3c112ef69924d8f8 100644
--- a/ash/common/wm/dock/docked_window_layout_manager.h
+++ b/ash/common/wm/dock/docked_window_layout_manager.h
@@ -16,6 +16,7 @@
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/observer_list.h"
+#include "base/scoped_observer.h"
 #include "base/time/time.h"
 #include "ui/aura/window_observer.h"
 #include "ui/display/display_observer.h"
@@ -23,6 +24,10 @@
 #include "ui/keyboard/keyboard_controller_observer.h"
 #include "ui/wm/public/activation_change_observer.h"
 
+namespace keyboard {
+class KeyboardController;
+}
+
 namespace ash {
 class DockedBackgroundWidget;
 class DockedWindowLayoutManagerObserver;
@@ -161,6 +166,8 @@ class ASH_EXPORT DockedWindowLayoutManager
                                 WmWindow* root_window) override;
   void OnOverviewModeStarting() override;
   void OnOverviewModeEnded() override;
+  void OnVirtualKeyboardStateChanged(bool activated,
+                                     WmWindow* root_window) override;
 
  private:
   struct CompareMinimumHeight;
@@ -315,6 +322,10 @@ class ASH_EXPORT DockedWindowLayoutManager
   // Observers of dock bounds changes.
   base::ObserverList<DockedWindowLayoutManagerObserver> observer_list_;
 
+  ScopedObserver<keyboard::KeyboardController,
+                 keyboard::KeyboardControllerObserver>
+      keyboard_observer_;
+
   DISALLOW_COPY_AND_ASSIGN(DockedWindowLayoutManager);
 };