Implement workspace scrubbing

ash/wm/workspace/workspace_manager.h

Index: ash/wm/workspace/workspace_manager.h
diff --git a/ash/wm/workspace/workspace_manager.h b/ash/wm/workspace/workspace_manager.h
index e59eada1c6ea9d7d1c4898926fc050fcfde8b101..8d3c63a0677f64076661f47e8feaa529f2b52571 100644
--- a/ash/wm/workspace/workspace_manager.h
+++ b/ash/wm/workspace/workspace_manager.h
@@ -78,9 +78,25 @@ class ASH_EXPORT WorkspaceManager : public ash::ShellObserver {
   // when a new Window is being added.
   aura::Window* GetParentForNewWindow(aura::Window* window);
 
+  // Called by the workspace cycler to hide the active workspace and activate
+  // the next unhidden workspace. The active workspace is moved to
+  // |hidden_workspaces_|.
+  // Returns false if the active workspace is the desktop workspace which
+  // cannot be hidden.
+  bool CycleToNextUnhiddenWorkspace();
+
+  // Called by the workspace cycler to activate the workspace in
+  // |hidden_workspaces_| which was most recently added. Activating the
+  // workspace moves it to |workspaces_|.
+  // Returns false if |hidden_workspaces| is empty.
+  bool CycleToNextHiddenWorkspace();
+
   // Starts the animation that occurs on first login.
   void DoInitialAnimation();
 
+  // Returns the window of the currently active workspace.
+  aura::Window* GetActiveWorkspaceWindow() const;
+
   // ShellObserver overrides:
   virtual void OnAppTerminating() OVERRIDE;
 
@@ -137,11 +153,11 @@ class ASH_EXPORT WorkspaceManager : public ash::ShellObserver {
 
   // Moves all the non-maximized child windows of |workspace| to the desktop
   // stacked beneath |stack_beneath| (if non-NULL). After moving child windows
-  // if |workspace| contains no children it is deleted, otherwise it it moved to
-  // |pending_workspaces_|.
-  void MoveWorkspaceToPendingOrDelete(Workspace* workspace,
-                                      aura::Window* stack_beneath,
-                                      SwitchReason reason);
+  // if |workspace| contains no children it is deleted. Otherwise, it is moved
+  // to |hidden_workspaces_|.
+  void MoveWorkspaceToHiddenOrDelete(Workspace* workspace,
+                                     aura::Window* stack_beneath,
+                                     SwitchReason reason);
 
   // Moves the children of |window| to the desktop. This excludes certain
   // windows. If |stack_beneath| is non-NULL the windows are stacked beneath it.
@@ -207,11 +223,14 @@ class ASH_EXPORT WorkspaceManager : public ash::ShellObserver {
   // which identifies the desktop.
   Workspaces workspaces_;
 
-  // The set of workspaces not currently active. Workspaces ended up here in
-  // two scenarios:
-  // . Prior to adding a window a new worskpace is created for it. The
-  //   Workspace is added to this set.
-  // . When the maximized window is minimized the workspace is added here.
+  // List of inactive workspaces which were deactivated as a result of a user
+  // action. Workspaces are moved here from |workspaces_| when the workspace's
+  // maximized window is minimized or hidden. The workspace is moved back to
+  // |workspaces_| when one of its windows is activated.
+  Workspaces hidden_workspaces_;
+
+  // Set of workspaces that have never been activated. Workspaces for new
+  // windows prior to those windows being activated are added to this set.
   // Once any window in the workspace is activated the workspace is moved to
   // |workspaces_|.
   std::set<Workspace*> pending_workspaces_;
@@ -219,10 +238,10 @@ class ASH_EXPORT WorkspaceManager : public ash::ShellObserver {
   // Owned by the Shell. May be NULL.
   ShelfLayoutManager* shelf_;
 
-  // Whether or not we're in MoveWorkspaceToPendingOrDelete(). As
-  // MoveWorkspaceToPendingOrDelete() may trigger another call to
-  // MoveWorkspaceToPendingOrDelete() we use this to avoid doing anything if
-  // already in MoveWorkspaceToPendingOrDelete().
+  // Whether or not we're in MoveWorkspaceToHiddenOrDelete(). As
+  // MoveWorkspaceToHiddenOrDelete() may trigger another call to
+  // MoveWorkspaceToHiddenOrDelete() we use this to avoid doing anything if
+  // already in MoveWorkspaceToHiddenOrDelete().
   bool in_move_;
 
   // Ideally we would delete workspaces when not needed. Unfortunately doing so