Move timeline and importers to use telemetry.value.TraceValue

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 5b285151eecb8ef4f772540080ac470931f53b3f..7998954b0161310cdee93a176bd467c03379eb77 100644
--- a/tools/telemetry/telemetry/core/backends/chrome/tracing_backend.py
+++ b/tools/telemetry/telemetry/core/backends/chrome/tracing_backend.py
@@ -26,7 +26,7 @@ class TracingBackend(object):
         'ws://127.0.0.1:%i/devtools/browser' % devtools_port)
     self._category_filter = None
     self._nesting = 0
-    self._tracing_data = []
+    self._trace_events = []
     self._is_tracing_running = False
 
   @property
@@ -57,10 +57,11 @@ class TracingBackend(object):
     self._is_tracing_running = True
     return True
 
-  def StopTracing(self, timeout=30):
-    """ Stops tracing on the innermost (!) nested call, because we cannot get
-        results otherwise. Resets _tracing_data on the outermost nested call.
-        Returns the result of the trace, as TracingTimelineData object.
+  def StopTracing(self, trace_value_builder, timeout=30):
+    """ Stops tracing and pushes reults to the provided TraceValueBuilder.
+
+    Tracing is stopped on the innermost (!) nested call, because we cannot get
+    results otherwise. Resets _trace_events on the outermost nested call.
     """
     self._nesting -= 1
     assert self._nesting >= 0
@@ -80,21 +81,13 @@ class TracingBackend(object):
             'seconds. If the trace data is big, you may want to increase the '
             'time out amount.' % err.elapsed_time)
       self._is_tracing_running = False
-    if self._nesting == 0:
-      self._category_filter = None
-      return self._GetTraceResultAndReset()
-    else:
-      return self._GetTraceResult()
 
-  def _GetTraceResult(self):
-    assert not self.is_tracing_running
-    return self._tracing_data
+    trace_value_builder.AddEventsTo(
+        trace_value_module.CHROME_TRACE_PART, self._trace_events)
 
-  def _GetTraceResultAndReset(self):
-    result = self._GetTraceResult()
-
-    self._tracing_data = []
-    return result
+    if self._nesting == 0:
+      self._category_filter = None
+      self._trace_events = []
 
   def _ErrorHandler(self, elapsed):
     logging.error('Unrecoverable error after %ds reading tracing response.',
@@ -105,9 +98,9 @@ class TracingBackend(object):
     if 'Tracing.dataCollected' == res.get('method'):
       value = res.get('params', {}).get('value')
       if type(value) in [str, unicode]:
-        self._tracing_data.append(value)
+        self._trace_events.append(value)
       elif type(value) is list:
-        self._tracing_data.extend(value)
+        self._trace_events.extend(value)
       else:
         logging.warning('Unexpected type in tracing data')
     elif 'Tracing.tracingComplete' == res.get('method'):