Remove the weak dictionary that maps tab objects to it markers

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

Index: tools/telemetry/telemetry/core/backends/chrome/tracing_backend.py
diff --git a/tools/telemetry/telemetry/core/backends/chrome/tracing_backend.py b/tools/telemetry/telemetry/core/backends/chrome/tracing_backend.py
index 9050c2f63091ed52fd0d61574e073dc02fdffd6e..7717df6459ddf4e4bed8ce43aa66da046acb7462 100644
--- a/tools/telemetry/telemetry/core/backends/chrome/tracing_backend.py
+++ b/tools/telemetry/telemetry/core/backends/chrome/tracing_backend.py
@@ -4,10 +4,8 @@
 
 import logging
 import re
-import weakref
 
 from telemetry.core.backends.chrome import inspector_websocket
-from telemetry.core.backends.chrome import tracing_timeline_data
 
 
 # All tracing categories not disabled-by-default
@@ -109,10 +107,6 @@ class TracingBackend(object):
     self._category_filter = None
     self._nesting = 0
     self._tracing_data = []
-    # Use a WeakKeyDictionary, because an ordinary dictionary could keep
-    # references to Tab objects around until it gets garbage collected.
-    # This would prevent telemetry from navigating to another page.
-    self._tab_to_marker_mapping = weakref.WeakKeyDictionary()
 
   @property
   def is_tracing_running(self):
@@ -164,14 +158,11 @@ class TracingBackend(object):
 
   def _GetTraceResult(self):
     assert not self.is_tracing_running
-    return tracing_timeline_data.TracingTimelineData(
-        self._tracing_data, self._tab_to_marker_mapping)
+    return self._tracing_data
 
   def _GetTraceResultAndReset(self):
     result = self._GetTraceResult()
-    # Reset tab to marker mapping for the next tracing run. Don't use clear(),
-    # because a TraceResult may still hold a reference to the dictionary object.
-    self._tab_to_marker_mapping = weakref.WeakKeyDictionary()
+
     self._tracing_data = []
     return result