SyncFS v2: Don't send file change event if action is none

BUG=240165
TEST=manual
R=tzik@chromium.org

Review URL: https://codereview.chromium.org/98113002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238022 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238022