Rename AlternateNavURLFetcher to OmniboxNavigationObserver in preparation for
expanding its scope.

BUG=151044
TEST=none
R=sky@chromium.org

Review URL: https://codereview.chromium.org/25963002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227074 0039d316-1c4b-4281-b951-d872f2087c98
split owner and web_contents access to diagnose a bug

BUG=283720

Review URL: https://codereview.chromium.org/25398004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227075 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227075