Add GetThreadToInteractionRecordsMapsFromModel method to timeline_interaction_record.

tools/perf/metrics/timeline.py

Index: tools/perf/metrics/timeline.py
diff --git a/tools/perf/metrics/timeline.py b/tools/perf/metrics/timeline.py
index 19db3d59ad1985c1cebcc645f45719e60ae55cb0..bd292e382219c3bf7708a7a4faf301f9625d2405 100644
--- a/tools/perf/metrics/timeline.py
+++ b/tools/perf/metrics/timeline.py
@@ -12,12 +12,14 @@ class LoadTimesTimelineMetric(timeline_based_metric.TimelineBasedMetric):
     super(LoadTimesTimelineMetric, self).__init__()
     self.report_main_thread_only = True
 
-  def AddResults(self, model, renderer_thread, interaction_records, results):
+  def AddResults(self, model, interaction_records, results):
     assert model
     assert len(interaction_records) == 1, (
       'LoadTimesTimelineMetric cannot compute metrics for more than 1 time '
       'range.')
+    self.VerifyAllRecordsIssuedBySameThread(interaction_records)
     interaction_record = interaction_records[0]
+    renderer_thread = interaction_record.async_event.start_thread
     if self.report_main_thread_only:
       thread_filter = 'CrRendererMain'
     else:
@@ -224,7 +226,7 @@ class ThreadTimesTimelineMetric(timeline_based_metric.TimelineBasedMetric):
         count += 1
     return count
 
-  def AddResults(self, model, _, interaction_records, results):
+  def AddResults(self, model, interaction_records, results):
     # Set up each thread category for consistant results.
     thread_category_results = {}
     for name in TimelineThreadCategories.values():