Moves WorkspaceEventHandler to ash/common

ash/mus/move_event_handler.h

Index: ash/mus/move_event_handler.h
diff --git a/ash/mus/move_event_handler.h b/ash/mus/move_event_handler.h
index a51caf1b707fdfa234f85c7257122e37c9bad0e1..b5aab75a646edb6155b264f7ae23ea43f82c0082 100644
--- a/ash/mus/move_event_handler.h
+++ b/ash/mus/move_event_handler.h
@@ -26,9 +26,13 @@ namespace ash {
 namespace mus {
 
 class WmWindowMus;
+class WorkspaceEventHandlerMus;
 
 // EventHandler attached to windows that may be dragged and/or resized. This
 // forwards to WmToplevelWindowEventHandler to handle the actual drag/resize.
+//
+// TODO(sky): rename this class to better reflect that it handles redirecting
+// events in addition to drag.
 class MoveEventHandler : public ui::EventHandler, public aura::WindowObserver {
  public:
   MoveEventHandler(ui::Window* mus_window,
@@ -59,6 +63,10 @@ class MoveEventHandler : public ui::EventHandler, public aura::WindowObserver {
   // Removes observer and EventHandler installed on |root_window_|.
   void Detach();
 
+  // Returns the WorkspaceEventHandlerMus, or null if the window is not in a
+  // workspace.
+  WorkspaceEventHandlerMus* GetWorkspaceEventHandlerMus();
+
   // Overridden from ui::EventHandler:
   void OnMouseEvent(ui::MouseEvent* event) override;
   void OnGestureEvent(ui::GestureEvent* event) override;