Coverity: Initialize target_message_loop_ in the constructor.

CID=3970
BUG=none
TEST=none
Review URL: http://codereview.chromium.org/233001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@26985 0039d316-1c4b-4281-b951-d872f2087c98
1 file changed