Add GetThreadToInteractionRecordsMapsFromModel method to timeline_interaction_record.

tools/perf/measurements/timeline_controller.py

Index: tools/perf/measurements/timeline_controller.py
diff --git a/tools/perf/measurements/timeline_controller.py b/tools/perf/measurements/timeline_controller.py
index 4cd0008b27de9fea89ba7ebe66f8e1593da1855e..b6381847d25e293006407bea970895ab78445ca0 100644
--- a/tools/perf/measurements/timeline_controller.py
+++ b/tools/perf/measurements/timeline_controller.py
@@ -49,15 +49,18 @@ class TimelineController(object):
     # Stop tracing.
     timeline_data = tab.browser.StopTracing()
     self._model = TimelineModel(timeline_data)
-    self._renderer_process = self._model.GetRendererProcessFromTabId(tab.id)
-    renderer_thread = self.model.GetRendererThreadFromTabId(tab.id)
-
+    threads_to_records_map = (
+        tir_module.GetThreadToInteractionRecordsMapsFromModel(
+            self._model))
+    assert len(threads_to_records_map) == 1, (
+        'timeline metrics only support interaction records issued from'
+        'a single thread.')
+    renderer_thread = threads_to_records_map.keys()[0]
+    interaction_records = threads_to_records_map.values()[0]
+    self._renderer_process = renderer_thread.parent
     run_smooth_actions_record = None
     self._smooth_records = []
-    for event in renderer_thread.async_slices:
-      if not tir_module.IsTimelineInteractionRecord(event.name):
-        continue
-      r = tir_module.TimelineInteractionRecord.FromAsyncEvent(event)
+    for r in interaction_records:
       if r.label == RUN_SMOOTH_ACTIONS:
         assert run_smooth_actions_record is None, (
           'TimelineController cannot issue more than 1 %s record' %