[Telemetry] Move gpu_timeline metrics to telemetry.web_perf

tools/perf/metrics/timeline_unittest.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.
 
 import unittest
 
-from metrics import test_page_test_results
 from metrics import timeline
+from telemetry.unittest_util import test_page_test_results
 from telemetry.timeline import model as model_module
 from telemetry.web_perf import timeline_interaction_record as tir_module
 
 def _GetInteractionRecord(start, end):
   return tir_module.TimelineInteractionRecord("test-record", start, end)
 
 
 class LoadTimesTimelineMetric(unittest.TestCase):
   def GetResults(self, metric, model, renderer_thread, interaction_records):
     results = test_page_test_results.TestPageTestResults(self)
@@ skipping 159 matching lines @@
     metric.details_to_report = timeline.ReportMainThreadOnly
     results = self.GetResults(metric, model, renderer_main.parent,
                               [_GetInteractionRecord(10, 30)])
 
     # Test a couple specific results.
     assert_results = {
       timeline.ThreadCpuTimeResultName('renderer_main') : 9.0,
     }
     for name, value in assert_results.iteritems():
       results.AssertHasPageSpecificScalarValue(name, 'ms', value)