telemetry: Add GetRendererProcessFromTab to timeline model.

tools/telemetry/telemetry/core/backends/chrome/trace_result.py

Index: tools/telemetry/telemetry/core/backends/chrome/trace_result.py
diff --git a/tools/telemetry/telemetry/core/backends/chrome/trace_result.py b/tools/telemetry/telemetry/core/backends/chrome/trace_result.py
index bcbcc3a26707671c4351a29c05a16bb8ce95e12e..000d32bc291b414949814001cee9342e95d81fb4 100644
--- a/tools/telemetry/telemetry/core/backends/chrome/trace_result.py
+++ b/tools/telemetry/telemetry/core/backends/chrome/trace_result.py
@@ -3,14 +3,27 @@
 # found in the LICENSE file.
 
 class TraceResult(object):

[nduca, 2013/10/31 07:32:02]

So okay, I remember now why impl was there. We've got to undo the change you
made.

TraceResult is a public class. Its in the wrong place here. It should be in
core/trace_result.py

We have a rule in telemetry that you dont subclass public classes for their
implementation. If you look, for instance, browser has a backend object. That is
because if users do help(browser), they'll see the public methods for not only
Browser, but also its implementation. Thats bad because it lets the backends
accidentally leak implementation-specific data up to the  user.

In this instance, you're actually doing that: ÅddTabToMarkerMapping for
instance, is really a backend implementation detail, but its now callable by
users. Thats not what we want.

What you probably want to do here is move this file as was before to
telemetyr/core/trace_results.py and keep the impl thing. AsTimelineModel shoudl
be unmodified.

The RawTraceResult and LegacyTraceResult should subclass from ChromeTraceResult,
and if it helped, you could call them ChromeRawTraceResult and
ChromeLegacyTraceResult. inside those two implementations, you make the base
have roughly the interface you have here, as was done before.

[ernstm, 2013/11/05 00:25:05]

Done.

-  def __init__(self, impl):
-    self._impl = impl
+  def __init__(self, tracing_data):
+    self._tracing_data = tracing_data
+    self._tab_to_marker_mapping = {}
 
   def Serialize(self, f):
     """Serializes the trace result to a file-like object"""
-    return self._impl.Serialize(f)
+    raise NotImplementedError()
 
   def AsTimelineModel(self):
     """Parses the trace result into a timeline model for in-memory

[nduca, 2013/10/31 07:32:02]

If you pass the marker mapping in to this constructor then you can add the
mappings right away and avoid the odd AddTabToBlah call on this that is visible
to users of the api.

[ernstm, 2013/11/05 00:25:05]

Done.

     manipulation."""
-    return self._impl.AsTimelineModel()
+    timeline = self._CreateTimelineModel()
+    for key, value in self._tab_to_marker_mapping.iteritems():
+      timeline_markers = timeline.FindTimelineMarkers(value)
+      assert(len(timeline_markers) == 1)
+      renderer_process = timeline_markers[0].start_thread.parent
+      timeline.AddMapping(key, renderer_process)
+    return timeline
+
+  def _CreateTimelineModel(self):
+    raise NotImplementedError()
+
+  def AddTabToMarkerMapping(self, tab, marker):
+    self._tab_to_marker_mapping[tab] = marker