GitLab

- Factor out SandboxOriginDatabase interface to SandboxOriginDatabaseInterface
- Implement SandboxIsolatedOriginDatabase which implements the same interface
  and only handles a single origin without database

BUG=242272
TEST=SandboxIsolatedOriginDatabaseTest.*
TEST=manually tested (launch Chrome w/o change, launch an app which uses HTML5 FS API, write some data -> launch Chrome with change, make sure the same contents appear & origin database's gone)
TBR=tzik@chromium.org

Review URL: https://codereview.chromium.org/16150002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@203139 0039d316-1c4b-4281-b951-d872f2087c98