Port PerfWarm startup test to Telemetry

tools/perf/perf_tools/startup_tests.py

+# Copyright (c) 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.page import page_benchmark
+
+# TODO(jeremy): Discard results from first iteration of warm tests.
+
+# Test how long Chrome takes to load when warm.
+class PerfWarm(page_benchmark.PageBenchmark):
+  def __init__(self):
+    super(PerfWarm, self).__init__(needs_browser_restart_after_each_run=True)
+
+  def CustomizeBrowserOptions(self, options):
+    options.AppendExtraBrowserArg('--dom-automation')
+    options.AppendExtraBrowserArg('--reduce-security-for-dom-automation-tests')
+
+  def MeasurePage(self, page, tab, results):
+    result = tab.EvaluateJavaScript("""
+      domAutomationController.getBrowserHistogram(
+          "Startup.BrowserMessageLoopStartTimeFromMainEntry")
+      """)
+    results.Add('startup_time', 'ms', result)