[telemetry] Add new benchmarks and rename them all.

tools/perf/benchmarks/startup.py

 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 from telemetry import test
 
 from measurements import startup
 
 
 class StartupColdBlankPage(test.Test):
+  tag = 'cold'
   test = startup.Startup
   page_set = 'page_sets/blank_page.json'
   options = {'cold': True,
              'pageset_repeat_iters': 5}
 
 
 class StartupWarmBlankPage(test.Test):
+  tag = 'warm'
   test = startup.Startup
   page_set = 'page_sets/blank_page.json'
   options = {'warm': True,
              'pageset_repeat_iters': 20}