(Merge to M-51) Revise the shelf alignment locking mechanism.

ash/wm/panels/attached_panel_window_targeter.cc

 // Copyright 2014 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.
 
 #include "ash/wm/panels/attached_panel_window_targeter.h"
 
 #include "ash/shelf/shelf.h"
 #include "ash/shell.h"
 #include "ash/wm/panels/panel_layout_manager.h"
 
@@ skipping 31 matching lines @@
   UpdateTouchExtend(root_window);
 }
 
 void AttachedPanelWindowTargeter::UpdateTouchExtend(aura::Window* root_window) {
   // Only update the touch insets for panels if they are attached to the shelf
   // in |root_window|.
   if (panel_container_->GetRootWindow() != root_window)
     return;
 
   DCHECK(panel_layout_manager_->shelf());
-
   gfx::Insets touch(default_touch_extend_);
-  switch (panel_layout_manager_->shelf()->alignment()) {
-    case SHELF_ALIGNMENT_BOTTOM:
-      touch = gfx::Insets(touch.top(), touch.left(), 0, touch.right());
-      break;
-    case SHELF_ALIGNMENT_LEFT:
-      touch = gfx::Insets(touch.top(), 0, touch.bottom(), touch.right());
-      break;
-    case SHELF_ALIGNMENT_RIGHT:
-      touch = gfx::Insets(touch.top(), touch.left(), touch.bottom(), 0);
-      break;
-  }
-
-  set_touch_extend(touch);
+  set_touch_extend(panel_layout_manager_->shelf()->SelectValueForShelfAlignment(
+      gfx::Insets(touch.top(), touch.left(), 0, touch.right()),
+      gfx::Insets(touch.top(), 0, touch.bottom(), touch.right()),
+      gfx::Insets(touch.top(), touch.left(), touch.bottom(), 0)));
 }
 
 }  // namespace ash