SyncFS: Add nested cases to LocalToRemoteSyncerTest


BUG=240165
TEST=unit_tests --gtest_filter=LocalToRemoteSyncerTest.*

Review URL: https://codereview.chromium.org/98383003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238067 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238067