Move telemetry/core/timeline and timeline_data to telemetry/timeline.

tools/perf/measurements/image_decoding.py

 # Copyright 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 metrics import power
 from telemetry.page import page_measurement
-from telemetry.core.timeline import model
+from telemetry.timeline import model
 
 
 class ImageDecoding(page_measurement.PageMeasurement):
   def __init__(self):
     super(ImageDecoding, self).__init__()
     self._power_metric = power.PowerMetric()
 
   def CustomizeBrowserOptions(self, options):
     options.AppendExtraBrowserArgs('--enable-gpu-benchmarking')
     power.PowerMetric.CustomizeBrowserOptions(options)
@@ skipping 40 matching lines @@
     assert durations, 'Failed to find "Decode Image" trace events.'
 
     image_decoding_avg = sum(durations) / len(durations)
     results.Add('ImageDecoding_avg', 'ms', image_decoding_avg)
     results.Add('ImageLoading_avg', 'ms',
                 tab.EvaluateJavaScript('averageLoadingTimeMs()'))
 
   def CleanUpAfterPage(self, page, tab):
     if tab.browser.is_tracing_running:
       tab.browser.StopTracing()