Remove unused |context| from GetDefaultParent().

ash/common/wm/container_finder.h

 // Copyright 2016 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_COMMON_WM_CONTAINER_FINDER_H_
 #define ASH_COMMON_WM_CONTAINER_FINDER_H_
 
 #include <vector>
 
 #include "ash/ash_export.h"
 
 namespace aura {
 class Window;
 }
 
 namespace gfx {
 class Rect;
 }
 
 namespace ash {
 
 class WmWindow;
 
 namespace wm {
 
 // Returns the first ancestor of |window| that has a known container ID.
 ASH_EXPORT WmWindow* GetContainerForWindow(WmWindow* window);
 
-// Returns the parent to add |window| to in |context|. This is generally
-// used when a window is moved from one root to another. In this case |context|
-// is the new root to add |window| to.
-ASH_EXPORT WmWindow* GetDefaultParent(WmWindow* context,
-                                      WmWindow* window,
+// Returns the parent to add |window| to. This is generally used when a window
+// is moved from one root to another.
+ASH_EXPORT WmWindow* GetDefaultParent(WmWindow* window,
                                       const gfx::Rect& bounds);
 
 // Returns the list of containers that match |container_id| in all root windows.
 // If |priority_root| is non-null, the container in |priority_root| is placed at
 // the front of the list.
 ASH_EXPORT std::vector<aura::Window*> GetContainersFromAllRootWindows(
     int container_id,
     aura::Window* priority_root = nullptr);
 
 }  // namespace wm
 }  // namespace ash
 
 #endif  // ASH_COMMON_WM_CONTAINER_FINDER_H_