Tracing v2: wire up stubs generated by the protozero protoc plugin

components/tracing/proto/event.proto

Index: components/tracing/proto/event.proto
diff --git a/components/tracing/proto/event.proto b/components/tracing/proto/event.proto
index 4be1b47ed846ecd97711d2e0a7d4a3202117d59a..f562850a27c16b9fd0c6febb13479b7a58d0ecdf 100644
--- a/components/tracing/proto/event.proto
+++ b/components/tracing/proto/event.proto
@@ -7,6 +7,27 @@ option optimize_for = LITE_RUNTIME;
 
 package tracing.proto;
 
+// Note on field numbers: fields in the range [1, 15] can be encoded using a
+// single byte preamble. Hence they should be used only for the most commonly
+// used fields fields (to save trace size). Use the range 16+ for fields that

[petrcermak, 2016/09/05 08:48:00]

nit: s/fields fields/fields/

[Primiano Tucci (use gerrit), 2016/09/05 09:37:44]

Done.

+// are not expected to be used frequently.
 message Event {
-  // TODO(kraynov): Make proto definitions.
+  enum EventType {

[petrcermak, 2016/09/05 08:48:00]

One would expect these to be sorted in an increasing order in value (77 < 88).
Not sure if protos forbid multiple enum values with the same name. If so, it's
going to be difficult to verify that there are no overlaps in the future (when
there are lots of event types).

[Primiano Tucci (use gerrit), 2016/09/05 09:37:44]

Done.
Ah good point. I can ask kraynov to add a check to its generator.

+    COMPLETE = 88;  // = 'X'

[petrcermak, 2016/09/05 08:48:00]

nit: add period at the end of comment? (not sure what the proto code style is)

[Primiano Tucci (use gerrit), 2016/09/05 09:37:44]

Done.

+    METADATA = 77;  // = 'M'

[petrcermak, 2016/09/05 08:48:00]

ditto

[Primiano Tucci (use gerrit), 2016/09/05 09:37:44]

Done.

+  };
+
+  optional EventType type = 1;
+
+  oneof name {
+    int64 name_id = 2;
+    string name_str = 16;
+  }
+
+  optional int64 category_id = 4;
+
+  optional uint64 timestamp = 5;
+  optional uint64 thread_timestamp = 6;
+
+  // TODO(primiano,kraynov): Add args and further fields in next CLs.
 }