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

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 99560e94643da9e141158b32ca069d9814e4fd0e..651b159061fd22e35cf90b1533d880e18dac0b7a 100644
--- a/ash/wm/workspace/workspace_manager.h
+++ b/ash/wm/workspace/workspace_manager.h
@@ -9,8 +9,8 @@
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
-#include "base/observer_list.h"
 #include "ash/ash_export.h"
+#include "ui/aura/window_observer.h"
 #include "ui/gfx/insets.h"
 #include "ui/gfx/size.h"
 
@@ -26,34 +26,32 @@ class Rect;
 namespace ash {
 namespace internal {
 class Workspace;
-class WorkspaceObserver;
+class WorkspaceManagerTest;
 
 // WorkspaceManager manages multiple workspaces in the desktop.
-class ASH_EXPORT WorkspaceManager {
+class ASH_EXPORT WorkspaceManager : public aura::WindowObserver{
  public:
   explicit WorkspaceManager(aura::Window* viewport);
   virtual ~WorkspaceManager();
 
-  // Returns the Window this WorkspaceManager controls.
-  aura::Window* contents_view() { return contents_view_; }
+  // Returns true if |window| should be managed by the WorkspaceManager.
+  bool IsManagedWindow(aura::Window* window) const;
 
-  // Create new workspace. Workspace objects are managed by
-  // this WorkspaceManager. Deleting workspace will automatically
-  // remove the workspace from the workspace_manager.
-  Workspace* CreateWorkspace();
+  // Adds/removes a window creating/destroying workspace as necessary.
+  void AddWindow(aura::Window* window);
+  void RemoveWindow(aura::Window* window);
 
-  // Returns the active workspace.
-  Workspace* GetActiveWorkspace() const;
+  // Activates the workspace containing |window|. Does nothing if |window| is
+  // NULL or not contained in a workspace.
+  void SetActiveWorkspaceByWindow(aura::Window* window);
 
-  // Returns the workspace that contanis the |window|.
-  Workspace* FindBy(aura::Window* window) const;
+  // Returns the Window this WorkspaceManager controls.
+  aura::Window* contents_view() { return contents_view_; }
 
   // Returns the window for rotate operation based on the |location|.
+  // TODO: this isn't currently used; remove if we do away with overview.
   aura::Window* FindRotateWindowForLocation(const gfx::Point& location);
 
-  // Sets the bounds of all workspaces.
-  void LayoutWorkspaces();
-
   // Returns the bounds in which a window can be moved/resized.
   gfx::Rect GetDragAreaBounds();
 
@@ -61,25 +59,9 @@ class ASH_EXPORT WorkspaceManager {
   void SetOverview(bool overview);
   bool is_overview() const { return is_overview_; }
 
-  // Rotate windows by moving |source| window to the position of |target|.
-  void RotateWindows(aura::Window* source, aura::Window* target);
-
   // Sets the size of a single workspace (all workspaces have the same size).
   void SetWorkspaceSize(const gfx::Size& workspace_size);
 
-  // Adds/Removes workspace observer.
-  void AddObserver(WorkspaceObserver* observer);
-  void RemoveObserver(WorkspaceObserver* observer);
-
-  // Returns true if this workspace manager is laying out windows.
-  // When true, LayoutManager must give windows their requested bounds.
-  bool layout_in_progress() const { return layout_in_progress_; }
-
-  // Sets the |layout_in_progress_| flag.
-  void set_layout_in_progress(bool layout_in_progress) {
-    layout_in_progress_ = layout_in_progress;
-  }
-
   // Sets/Returns the ignored window that the workspace manager does not
   // set bounds on.
   void set_ignored_window(aura::Window* ignored_window) {
@@ -87,23 +69,52 @@ class ASH_EXPORT WorkspaceManager {
   }
   aura::Window* ignored_window() { return ignored_window_; }
 
+  // Overriden from aura::WindowObserver:
+  virtual void OnWindowPropertyChanged(aura::Window* window,
+                                       const char* name,
+                                       void* old) OVERRIDE;
+
  private:
   friend class Workspace;
+  friend class WorkspaceManagerTest;
 
   void AddWorkspace(Workspace* workspace);
   void RemoveWorkspace(Workspace* workspace);
 
+  // Create new workspace. Workspace objects are managed by
+  // this WorkspaceManager. Deleting workspace will automatically
+  // remove the workspace from the workspace_manager.
+  Workspace* CreateWorkspace();
+
+  // Returns the active workspace.
+  Workspace* GetActiveWorkspace() const;
+
+  // Returns the workspace that contanis the |window|.
+  Workspace* FindBy(aura::Window* window) const;
+
   // Sets the active workspace.
   void SetActiveWorkspace(Workspace* workspace);
 
-  // Returns the bounds of the work are given |workspace_bounds|.
-  gfx::Rect GetWorkAreaBounds(const gfx::Rect& workspace_bounds);
+  // Returns the bounds of the work area.
+  gfx::Rect GetWorkAreaBounds();
 
   // Returns the index of the workspace that contains the |window|.
   int GetWorkspaceIndexContaining(aura::Window* window) const;
 
-  // Update contents_view size and move the viewport to the active workspace.
-  void UpdateContentsView();
+  // Sets the bounds of |window|. This sets |ignored_window_| to |window| so
+  // that the bounds change is allowed through.
+  void SetWindowBounds(aura::Window* window, const gfx::Rect& bounds);
+
+  // Resets the bounds of |window| to its restored bounds (if set), ensuring
+  // it fits in the the windows current workspace.
+  void SetWindowBoundsFromRestoreBounds(aura::Window* window);
+
+  // Invoked when the maximized state of |window| changes.
+  void MaximizedStateChanged(aura::Window* window);
+
+  // Returns the Workspace whose type is TYPE_NORMAL, or NULL if there isn't
+  // one.
+  Workspace* GetNormalWorkspace();
 
   aura::Window* contents_view_;
 
@@ -118,14 +129,9 @@ class ASH_EXPORT WorkspaceManager {
   // True if the workspace manager is in overview mode.
   bool is_overview_;
 
-  // True if this layout manager is laying out windows.
-  bool layout_in_progress_;
-
   // The window that WorkspaceManager does not set the bounds on.
   aura::Window* ignored_window_;
 
-  ObserverList<WorkspaceObserver> observers_;
-
   DISALLOW_COPY_AND_ASSIGN(WorkspaceManager);
 };