[Tracing] Export TraceConfig to model.metadata

tracing/tracing/extras/importer/trace_event_importer_test.html

Index: tracing/tracing/extras/importer/trace_event_importer_test.html
diff --git a/tracing/tracing/extras/importer/trace_event_importer_test.html b/tracing/tracing/extras/importer/trace_event_importer_test.html
index 98d1b6e7b4e0b9c2702a4ec67c9a2b4b0a252533..20eb115d42e2dc4ad9d22727c5741c9274a56fe2 100644
--- a/tracing/tracing/extras/importer/trace_event_importer_test.html
+++ b/tracing/tracing/extras/importer/trace_event_importer_test.html
@@ -5300,6 +5300,26 @@ tr.b.unittest.testSuite(function() {
     assert.equal(m.metadata[0].value, metadataValue);
   });
 
+  test('importTraceConfigAsMetadata', function() {
+    var traceConfigData = {
+        enable_argument_filter: false,
+        enable_sampling: false
+    };
+
+    var eventData = {
+      traceEvents: [
+      { name: 'TraceConfig', args: {value: traceConfigData },

[fmeawad, 2016/05/24 21:03:51]

Can you add a real example of a current TraceConfig so that we can set the
expectation on what is included?

nit: missing space ": { value"

[nednguyen, 2016/05/24 21:11:51]

This is from a real example:
"{"pid":16662,"tid":16662,"ts":1107984591957,"ph":"M","cat":"__metadata","name":"TraceConfig","args":{"value":{"enable_argument_filter":false,"enable_sampling":false,"enable_systrace":false,"record_mode":"record-until-full"}},"tts":340738944}"

+        pid: 2, ts: 0, tid: 1, ph: 'M' },
+      ],
+    };
+
+    var m = makeModel(eventData);
+    assert.isTrue(m.metadata instanceof Array);
+    assert.equal(m.metadata.length, 1);
+    assert.equal(m.metadata[0].name, 'TraceConfig');
+    assert.equal(m.metadata[0].value, traceConfigData);
+  });
+
   test('importMarks', function() {
     var eventData = {
       traceEvents: [