Update Maps pixel test.

content/test/gpu/gpu_tests/maps.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.
 
 """Runs a Google Maps pixel test.
 Performs several common navigation actions on the map (pan, zoom, rotate) then
 captures a screenshot and compares selected pixels against expected values"""
 
 import json
 import os
@@ skipping 25 matching lines @@
     # safe to do so.
     MapsValidator.SpinWaitOnRAF(tab, 3)
 
     if not tab.screenshot_supported:
       raise page_test.Failure('Browser does not support screenshot capture')
     screenshot = tab.Screenshot(5)
     if screenshot is None:
       raise page_test.Failure('Could not capture screenshot')
 
     dpr = tab.EvaluateJavaScript('window.devicePixelRatio')
+    print 'Maps\' devicePixelRatio is ' + str(dpr)
+    # Even though the Maps test uses a fixed devicePixelRatio so that
+    # it fetches all of the map tiles at the same resolution, on two
+    # different devices with the same devicePixelRatio (a Retina
+    # MacBook Pro and a Nexus 9), different scale factors of the final
+    # screenshot are observed. Hack around this by specifying a scale
+    # factor for these bots in the test expectations. This relies on
+    # the test-machine-name argument being specified on the command
+    # line.
     expected = self._ReadPixelExpectations(page)
     self._ValidateScreenshotSamples(
         page.display_name, screenshot, expected, dpr)
 
   @staticmethod
   def SpinWaitOnRAF(tab, iterations, timeout=60):
     waitScript = r"""
       window.__spinWaitOnRAFDone = false;
       var iterationsLeft = %d;
 
@@ skipping 17 matching lines @@
   def _ReadPixelExpectations(self, page):
     expectations_path = os.path.join(page._base_dir, page.pixel_expectations)
     with open(expectations_path, 'r') as f:
       json_contents = json.load(f)
     return json_contents
 
 
 class MapsPage(gpu_test_base.PageBase):
   def __init__(self, story_set, base_dir, expectations):
     super(MapsPage, self).__init__(
-        url='http://localhost:10020/tracker.html',
+        url='http://localhost:8000/performance.html',
         page_set=story_set,
         base_dir=base_dir,
-        name='Maps.maps_002',
+        name='Maps.maps_004',
         make_javascript_deterministic=False,
         expectations=expectations)
-    self.pixel_expectations = 'data/maps_002_expectations.json'
+    self.pixel_expectations = 'data/maps_004_expectations.json'
 
   def RunNavigateSteps(self, action_runner):
     super(MapsPage, self).RunNavigateSteps(action_runner)
     action_runner.WaitForJavaScriptCondition(
         'window.testDone', timeout_in_seconds=180)
 
 
 class Maps(cloud_storage_test_base.TestBase):
-  """Google Maps pixel tests."""
+  """Google Maps pixel tests.
+
+  Note: the WPR for this test was recorded from the smoothness.maps
+  benchmark's similar page. The Maps team gave us a build of their
+  test. The only modification to the test was to config.js, where the
+  width and height query args were set to 800 by 600. The WPR was
+  recorded with:
+
+  tools/perf/record_wpr smoothness_maps --browser=system --upload
+
+  Then the maps_???.wpr.sha1 and maps.json were copied from
+  tools/perf/page_sets/data into content/test/gpu/page_sets/data. The
+  same sha1 file and json file need to be copied into both of these
+  directories in any CL which updates the recording."""
   test = MapsValidator
 
   @classmethod
   def Name(cls):
     return 'maps'
 
   def _CreateExpectations(self):
     return maps_expectations.MapsExpectations()
 
   def CreateStorySet(self, options):
     story_set_path = os.path.join(
         path_util.GetChromiumSrcDir(), 'content', 'test', 'gpu', 'page_sets')
     ps = story_set_module.StorySet(
         archive_data_file='data/maps.json',
         base_dir=story_set_path,
         cloud_storage_bucket=story_module.PUBLIC_BUCKET)
     ps.AddStory(MapsPage(ps, ps.base_dir, self.GetExpectations()))
     return ps