[SyncFS] Implement LocalToRemoteSync non-conflict file update case.

BUG=240165
NOTRY=true

Review URL: https://codereview.chromium.org/76003005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236216 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236216