Add default browser checking and setting on Linux.
BUG=11972
TEST=none

Review URL: http://codereview.chromium.org/155100

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@20380 0039d316-1c4b-4281-b951-d872f2087c98
5 files changed