Making sure that SpeechRecognitionDispatcherHost is not used after free
A test have been discovered that under certain conditions a use after
free can occur.

BUG=339667

Review URL: https://codereview.chromium.org/170243005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252233 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252233