Add Quota related method to CannedSyncableFileSystem for testing

BUG=157789
TEST=SyncableFileSystemTest.SyncableLocalSandboxCombined

Review URL: https://codereview.chromium.org/11266031

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@164028 0039d316-1c4b-4281-b951-d872f2087c98
3 files changed