Add HasChangeListKind and HasFileListKind methods.

New methods will be used to figure out what is the returned JSON's type in
following CL.

BUG=224870
TEST=Ran unit_tests

Review URL: https://chromiumcodereview.appspot.com/14160002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@193642 0039d316-1c4b-4281-b951-d872f2087c98
3 files changed