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

ash/wm/window_util.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_WM_WINDOW_UTIL_H_
 #define ASH_WM_WINDOW_UTIL_H_
 #pragma once
 
 #include <set>
 
@@ skipping 31 matching lines @@
 // Maximizes |window|, which must not be NULL.
 ASH_EXPORT void MaximizeWindow(aura::Window* window);
 
 // Restores |window|, which must not be NULL.
 ASH_EXPORT void RestoreWindow(aura::Window* window);
 
 // Returns true if the set of |windows| contains a full-screen window.
 typedef std::set<aura::Window*> WindowSet;
 ASH_EXPORT bool HasFullscreenWindow(const WindowSet& windows);
 
+// Sets whether the window should be open in a split mode. Only applicable when
+// workspaces are used.
+ASH_EXPORT void SetOpenWindowSplit(aura::Window* window, bool value);
+ASH_EXPORT bool GetOpenWindowSplit(aura::Window* window);
+
 }  // namespace window_util
 }  // namespace ash
 
 #endif  // ASH_WM_WINDOW_UTIL_H_