Add a 4k 60 fps vp9 smpte bars video to telemetry tests.

This video is 10 seconds of SMPTE color bars.
The load on the vp9 decoder is relatively low, in this way we can better
measure the load on the compositor.

The video has been generated using libavfilter.
BUG=

Review URL: https://codereview.chromium.org/1083073003

Cr-Commit-Position: refs/heads/master@{#329332}

tools/perf/metrics/system_memory.py

@@ -117,7 +117,7 @@ def _SubtractMemoryStats(end_memory_stats, start_memory_stats):
     else:
       for metric in end_process_memory:
         end_value = end_process_memory[metric]
-        start_value = start_memory_stats[process_type][metric] or 0
+        start_value = start_memory_stats[process_type].get(metric, 0)
         if 'Peak' in metric:
           memory_stats[process_type][metric] = end_value
         else:

tools/perf/page_sets/tough_video_cases.py

@@ -485,6 +485,19 @@ class Page35(ToughVideoCasesPage):
   def RunPageInteractions(self, action_runner):
     self.SeekBeforeAndAfterPlayhead(action_runner)
 
+class Page36(ToughVideoCasesPage):
+
+  def __init__(self, page_set):
+    super(Page36, self).__init__(
+      url=('file://tough_video_cases/video.html?src='
+           'smpte_3840x2160_60fps_vp9.webm'),
+      page_set=page_set)
+
+    self.add_browser_metrics = True
+
+  def RunPageInteractions(self, action_runner):
+    self.SeekBeforeAndAfterPlayhead(action_runner)
+
 class ToughVideoCasesPageSet(page_set_module.PageSet):
 
   """
@@ -529,3 +542,4 @@ class ToughVideoCasesPageSet(page_set_module.PageSet):
     self.AddUserStory(Page33(self))
     self.AddUserStory(Page34(self))
     self.AddUserStory(Page35(self))
+    self.AddUserStory(Page36(self))

tools/perf/page_sets/tough_video_cases/smpte_3840x2160_60fps_vp9.webm.sha1

+ce653f28b96767a28c10be10a793bbc3742be888
\ No newline at end of file