[SyncFS] Run ConflictResolver more frequently.

BUG=240165

Review URL: https://codereview.chromium.org/106293002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238952 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238952