Reworks the workspace code. Here's the new heuristics:

ash/wm/workspace_controller.h

Index: ash/wm/workspace_controller.h
diff --git a/ash/wm/workspace_controller.h b/ash/wm/workspace_controller.h
index 2d65e4238d7166dbd1c1dad5e9f2af4bb0c12281..9e541d984f45720e9a1489ae4478d18113c1e56a 100644
--- a/ash/wm/workspace_controller.h
+++ b/ash/wm/workspace_controller.h
@@ -7,7 +7,6 @@
 #pragma once
 
 #include "ash/launcher/launcher_model_observer.h"
-#include "ash/wm/workspace/workspace_observer.h"
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/aura/root_window_observer.h"
@@ -35,7 +34,6 @@ class WorkspaceManager;
 class ASH_EXPORT WorkspaceController :
       public aura::RootWindowObserver,
       public aura::WindowObserver,
-      public ash::internal::WorkspaceObserver,
       public ash::LauncherModelObserver {
  public:
   explicit WorkspaceController(aura::Window* workspace_viewport);
@@ -58,13 +56,6 @@ class ASH_EXPORT WorkspaceController :
                                        const char* key,
                                        void* old) OVERRIDE;
 
-  // WorkspaceObserver overrides:
-  virtual void WindowMoved(WorkspaceManager* manager,
-                           aura::Window* source,
-                           aura::Window* target) OVERRIDE;
-  virtual void ActiveWorkspaceChanged(WorkspaceManager* manager,
-                                      Workspace* old) OVERRIDE;
-
   // Invoked after an item has been added to the model.
   virtual void LauncherItemAdded(int index) OVERRIDE;
   virtual void LauncherItemRemoved(int index) OVERRIDE;