Added GPU performance metrics.

tools/perf/benchmarks/gpu_times.py

+# Copyright 2015 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 benchmarks import silk_flags
+from measurements import gpu_times
+import page_sets
+from telemetry import benchmark
+
+
+class _GPUTimes(benchmark.Benchmark):
+  def CreatePageTest(self, options):
+    return gpu_times.GPUTimes()
+
+
+@benchmark.Enabled('android')
+class GPUTimesKeyMobileSites(_GPUTimes):
+  """Measures GPU timeline metric on key mobile sites."""
+  page_set = page_sets.KeyMobileSitesSmoothPageSet
+
+
+class GPUTimesTop25Sites(_GPUTimes):
+  """Measures GPU timeline metric for the top 25 sites."""
+  page_set = page_sets.Top25SmoothPageSet