Implement workspace scrubbing

ash/wm/workspace/workspace.h

Index: ash/wm/workspace/workspace.h
diff --git a/ash/wm/workspace/workspace.h b/ash/wm/workspace/workspace.h
index 575a3683ebda79af79e6c9883d96c9689fbff914..18da71889098334caf8bd817709d612f35712044 100644
--- a/ash/wm/workspace/workspace.h
+++ b/ash/wm/workspace/workspace.h
@@ -55,9 +55,13 @@ class ASH_EXPORT Workspace {
   }
   WorkspaceManager* workspace_manager() { return workspace_manager_; }
 
-  // Returns true if the Workspace should be moved to pending. This is true
+  // Returns the active window if the active window is in this workspace.
+  // Otherwise, NULL is returned.
+  aura::Window* GetActiveWindow() const;
+
+  // Returns true if the Workspace should be moved to hidden. This is true
   // if there are no visible maximized windows.
-  bool ShouldMoveToPending() const;
+  bool ShouldMoveToHidden() const;
 
   // Returns the number of maximized windows (including minimized windows that
   // would be maximized on restore). This does not consider visibility.