Added support to listen on Network.responseReceived and expose that through tab.py

tools/telemetry/telemetry/core/timeline/model.py

Index: tools/telemetry/telemetry/core/timeline/model.py
diff --git a/tools/telemetry/telemetry/core/timeline/model.py b/tools/telemetry/telemetry/core/timeline/model.py
index 974bd6141d90390b92b1464b623620db843f138d..4b578a6b82eadf7d030b796b28d78a947ea8401e 100644
--- a/tools/telemetry/telemetry/core/timeline/model.py
+++ b/tools/telemetry/telemetry/core/timeline/model.py
@@ -77,7 +77,7 @@ class TimelineModel(object):
   def browser_process(self, browser_process):
     self._browser_process = browser_process
 
-  def ImportTraces(self, traces, shift_world_to_zero=True):
+  def ImportTraces(self, traces, shift_world_to_zero=True, freeze=True):
     if self._frozen:
       raise Exception("Cannot add events once recording is done")
 
@@ -90,9 +90,10 @@ class TimelineModel(object):
     for importer in importers:
       # TODO: catch exceptions here and add it to error list
       importer.ImportEvents()
-    self.FinalizeImport(shift_world_to_zero, importers)
+    self.FinalizeImport(shift_world_to_zero, importers, freeze)
 
-  def FinalizeImport(self, shift_world_to_zero=False, importers=None):
+  def FinalizeImport(self, shift_world_to_zero=False, importers=None,
+                     freeze=True):
     if importers == None:
       importers = []
     self.UpdateBounds()
@@ -111,8 +112,11 @@ class TimelineModel(object):
       self.ShiftWorldToZero()
     self.UpdateBounds()
 
-    # Because of FinalizeImport, it would probably be a good idea
-    # to prevent the timeline from from being modified.
+    if freeze:
+      self.Freeze()
+
+  def Freeze(self):
+    # Prevent the timeline from from being modified.
     self._frozen = True
 
   def ShiftWorldToZero(self):