Remove layout metrics in thread_times benchmarks

These metrics were added a long time ago and seem not very useful. They are also
using the legacy TBMv1 metrics structure in a not well supported way.

Bug: 775560, 760553
Change-Id: Iaa824a1fd8bcf9b24214904b33d9e4d730f63a42
Reviewed-on: https://chromium-review.googlesource.com/723919
Reviewed-by: Sunny Sachanandani <sunnyps@chromium.org>
Reviewed-by: Ben Hayden <benjhayden@chromium.org>
Commit-Queue: Ned Nguyen <nednguyen@google.com>
Cr-Commit-Position: refs/heads/master@{#509507}

tools/perf/measurements/thread_times.py

@@ -4,7 +4,6 @@
 
 from telemetry.page import legacy_page_test
 from telemetry.timeline import chrome_trace_category_filter
-from telemetry.web_perf.metrics import layout
 
 from measurements import timeline_controller
 from metrics import timeline
@@ -47,9 +46,6 @@ def ValidateAndMeasurePage(self, page, tab, results):
       metric.details_to_report = timeline.ReportSilkDetails
     metric.AddResults(self._timeline_controller.model, renderer_thread,
                       self._timeline_controller.smooth_records, results)
-    layout_metric = layout.LayoutMetric()
-    layout_metric.AddResults(self._timeline_controller.model, renderer_thread,
-                             self._timeline_controller.smooth_records, results)
 
   def DidRunPage(self, platform):
     if self._timeline_controller: