aura: Handle NULL |container| case in GetTopmostWindowToActivate

When shell shutdown starts, if the active window is in a container that gets
destructed after the default container (e.g. status area widget, full screen
bubble), GetTopmostWindowToActivate will be called when destructing this active
window. However, GetContainer(kShellWindowId_DefaultContainer) would return NULL
because default container is already destructed at this point.

Add a NULL check to avoid the crash.

BUG=110916
TEST=Verify the crash in issue 110916 no longer happens.


Review URL: http://codereview.chromium.org/9169058

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@119190 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 11 insertions, 6 deletions

diff --git a/ash/wm/activation_controller.cc b/ash/wm/activation_controller.cc
index 8f4e801..dda4b75 100644
--- a/ash/wm/activation_controller.cc
+++ b/ash/wm/activation_controller.cc
@@ -209,12 +209,17 @@ aura::Window* ActivationController::GetTopmostWindowToActivate(
   const aura::Window* container =
       default_container_for_test_ ? default_container_for_test_ :
           GetContainer(kShellWindowId_DefaultContainer);
-  for (aura::Window::Windows::const_reverse_iterator i =
-           container->children().rbegin();
-       i != container->children().rend();
-       ++i) {
-    if (*i != ignore && CanActivateWindow(*i))
-      return *i;
+  // When destructing an active window that is in a container destructed after
+  // the default container during shell shutdown, |container| would be NULL
+  // because default container is destructed at this point.
+  if (container) {
+    for (aura::Window::Windows::const_reverse_iterator i =
+             container->children().rbegin();
+         i != container->children().rend();
+         ++i) {
+      if (*i != ignore && CanActivateWindow(*i))
+        return *i;
+    }
   }
   return NULL;
 }