Benchmark to characterize main thread usage during load

tools/perf/perf_tools/loading_benchmark_unittest.py

+# Copyright (c) 2012 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 multi_page_benchmark_unittest_base
+from perf_tools import loading_benchmark
+
+class SmoothnessBenchmarkUnitTest(
+  multi_page_benchmark_unittest_base.MultiPageBenchmarkUnitTestBase):
+
+  def testBasicFunctionality(self):
+    ps = self.CreatePageSetFromFileInUnittestDataDir('blank.html')
+
+    benchmark = loading_benchmark.LoadingBenchmark()
+    all_results = self.RunBenchmark(benchmark, ps)
+
+    self.assertEqual(0, len(all_results.page_failures))
+    self.assertEqual(1, len(all_results.page_results))
+
+    results0 = all_results.page_results[0]
+    self.assertTrue(results0['Layout'].value > 0)
+    self.assertTrue(results0['Paint'].value > 0)