Use the correct signal to detect failed navigations

BUG=50943
TEST=unit_tests:FrameNavigationStateTest.*, browser_tests:ExtensionApiTest.WebNavigation*

Review URL: http://codereview.chromium.org/5290005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@67999 0039d316-1c4b-4281-b951-d872f2087c98
6 files changed