Fix a crash on closing cookies and site info bubble.

Add NULL check for window in GetNativeThemeForWindow() to avoid a crash.

BUG=367698

Review URL: https://codereview.chromium.org/258953004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@266989 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/ui/aura/chrome_browser_main_extra_parts_aura.cc

@@ -44,6 +44,9 @@ namespace {
 
 #if defined(OS_LINUX) && !defined(OS_CHROMEOS)
 ui::NativeTheme* GetNativeThemeForWindow(aura::Window* window) {
+  if (!window)
+    return NULL;
+
   Profile* profile = NULL;
   if (window->type() == ui::wm::WINDOW_TYPE_NORMAL ||
       window->type() == ui::wm::WINDOW_TYPE_POPUP) {