Disable SaveUserImageFromProfileImage and ProfileImageDownloadDoesNotClobber tests

TBR=bartfab
BUG=327775

Review URL: https://codereview.chromium.org/105693014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240181 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240181
Code to contact webstore backend for extension install verification

This also cleans up a case where we could end up asking for verification
of items that aren't extensions, or do extra work because we weren't
remembering an empty signature if there weren't any extensions to verify. 

BUG=318776

Review URL: https://codereview.chromium.org/111953002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240182 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240182