Make TestResultsServer use master url names instead of class names.

This replaces: https://codereview.chromium.org/421593008/

The old-style names (e.g., ChromiumWin) are not canonical, and can't
be used to construct a URL to query the buildbot master.  Switch to
the canonical names (e.g., chromium.win).

After this lands, the flakiness dashboard should be updated to start
querying files by the new names; then all of the deprecated_name
sleight of hand should be removed here.

R=ojan@chromium.org
TEST=model/jsonresults_unittest.py
NOTRY=true

Review URL: https://codereview.chromium.org/418223016

git-svn-id: svn://svn.chromium.org/blink/trunk@179509 bbb929c8-8fbe-4397-9dbb-9b2b20218538