Retrieve per host storage usage from QuotaManager.

R=kinuko@chromium.org
BUG=none
TEST=QuotaManagerTest.GetUsage

Review URL: http://codereview.chromium.org/8079004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@103921 0039d316-1c4b-4281-b951-d872f2087c98
  void set_quota_manager(QuotaManager* quota_manager) {
    quota_manager_ = quota_manager;
  }

  void set_quota_manager(QuotaManager* quota_manager) {
    quota_manager_ = quota_manager;
  }
