Switch default WM mode to managed

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 2413c4b2cf3a3fe9288f82a25ca593288d46fbb9..b3c34ed9e411d62a35dea3cd474c40214115c0f8 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -222,6 +222,9 @@ class ASH_EXPORT Shell {
   }
 
  private:
+  FRIEND_TEST_ALL_PREFIXES(RootWindowEventFilterTest, MouseEventCursors);
+  FRIEND_TEST_ALL_PREFIXES(RootWindowEventFilterTest, TransformActivate);
+
   typedef std::pair<aura::Window*, gfx::Rect> WindowAndBoundsPair;
 
   explicit Shell(ShellDelegate* delegate);
@@ -242,6 +245,9 @@ class ASH_EXPORT Shell {
   // has the effect of deleting the current LayoutManager.
   void ResetLayoutManager(int container_id);
 
+  // Disables the workspace grid layout.
+  void DisableWorkspaceGridLayout();
+
   static Shell* instance_;
 
   // Window mode is computed at shell initialization time, so allow it to be