Give a document icon to Chromium for file types it can view when preview is turned off.

BUG=19763
TEST=per bug. This might not appear to work given how LaunchServices caches and registers applications. You may need to test on a totally clean machine.
Review URL: http://codereview.chromium.org/194116

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@26248 0039d316-1c4b-4281-b951-d872f2087c98