Fix crash when dragging a half width window to split view from overivew mode

athena/wm/window_manager_impl.h

Index: athena/wm/window_manager_impl.h
diff --git a/athena/wm/window_manager_impl.h b/athena/wm/window_manager_impl.h
index c8e9038dac5f144003d33442192508bfb10878dd..f5d0ae9af0d3f4b2c6aa89b96aed7ca9dda2dd8d 100644
--- a/athena/wm/window_manager_impl.h
+++ b/athena/wm/window_manager_impl.h
@@ -20,6 +20,10 @@ class WMState;
 
 namespace athena {
 
+namespace test {
+class WindowManagerImplTestApi;
+}
+
 class BezelController;
 class SplitViewController;
 class WindowListProvider;
@@ -39,7 +43,7 @@ class WindowManagerImpl : public WindowManager,
   virtual bool IsOverviewModeActive() OVERRIDE;
 
  private:
-  friend class WindowManagerImplTestApi;
+  friend class test::WindowManagerImplTestApi;
   friend class AthenaContainerLayoutManager;
 
   enum Command {