Lock screen for Chrome-Athena

athena/wm/window_overview_mode.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 "athena/wm/window_overview_mode.h"
 
 #include <complex>
 #include <vector>
 
 #include "athena/wm/overview_toolbar.h"
@@ skipping 412 matching lines @@
     while (!targeter && window->GetParentTarget()) {
       window = window->GetParentTarget();
       targeter = window->GetEventTargeter();
     }
     if (!targeter)
       return NULL;
     aura::Window* target = static_cast<aura::Window*>(
         targeter->FindTargetForLocatedEvent(container_, event));
     while (target && target->parent() != container_)
       target = target->parent();
-    aura::Window* transient_parent = wm::GetTransientParent(target);
+    aura::Window* transient_parent =
+        target ? wm::GetTransientParent(target) : NULL;
     return transient_parent ? transient_parent : target;
   }
 
   // Scroll the window list by |delta_y| amount. |delta_y| is negative when
   // scrolling up; and positive when scrolling down.
   void DoScroll(float delta_y) {
     const float kEpsilon = 1e-3f;
     float delta_y_p = std::abs(delta_y) / GetScrollableHeight();
     const aura::Window::Windows& windows =
         window_list_provider_->GetWindowList();
@@ skipping 414 matching lines @@
     aura::Window* container,
     WindowListProvider* window_list_provider,
     SplitViewController* split_view_controller,
     WindowOverviewModeDelegate* delegate) {
   return scoped_ptr<WindowOverviewMode>(
       new WindowOverviewModeImpl(container, window_list_provider,
                                  split_view_controller, delegate));
 }
 
 }  // namespace athena