Make timeline_data indented JSON.

BUG=None
TEST=None

Review URL: https://codereview.chromium.org/315393004

Cr-Commit-Position: refs/heads/master@{#289028}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@289028 0039d316-1c4b-4281-b951-d872f2087c98

tools/telemetry/telemetry/timeline/inspector_timeline_data.py

@@ -14,7 +14,7 @@ class InspectorTimelineData(TimelineData):
   def Serialize(self, f):
     """Serializes the trace result to a file-like object"""
     f.write('{"traceEvents":')
-    json.dump(self._event_data, f)
+    json.dump(self._event_data, f, indent=4)
     f.write('}')
 
   def EventData(self):

tools/telemetry/telemetry/timeline/tracing_timeline_data.py

@@ -14,9 +14,9 @@ class TracingTimelineData(TimelineData):
   def Serialize(self, f):
     """Serializes the trace result to a file-like object"""
     if 'traceEvents' in self._event_data:
-      json.dump(self._event_data, f)
+      json.dump(self._event_data, f, indent=4)
     else:
-      json.dump({'traceEvents' : self._event_data}, f)
+      json.dump({'traceEvents' : self._event_data}, f, indent=4)
 
   def EventData(self):
     return self._event_data