Server Request Tests and Mock Promise Enhancements

Added some server request tests and improved the mock promise to handle
these tests. The Mock Promise now better simulates the full extent of
promises.

BUG=164227

Review URL: https://codereview.chromium.org/202293003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@258239 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed