LogDog: Update protobufs, add support library.

common/logdog/protocol/butler.proto

Index: common/logdog/protocol/butler.proto
diff --git a/common/logdog/protocol/butler.proto b/common/logdog/protocol/butler.proto
index aaea291e03fa96f3142f0eb4a3291c386823da7f..cf16766b06c1fa5be17aadb653d1a1a5bf603e69 100644
--- a/common/logdog/protocol/butler.proto
+++ b/common/logdog/protocol/butler.proto
@@ -8,6 +8,26 @@ import "log.proto";
 import "types.proto";
 
 /*
+ * ButlerMetadata appears as a frame at the beginning of Butler published data
+ * to describe the remainder of the contents.

[tandrii(chromium), 2015/08/11 17:41:37]

I'm not sure that's the best way to achieve what you want. Maybe ask
protobuf-gurus on our team? I'll let someone else approve this change.

[dnj, 2015/08/11 18:20:37]

What do you mean?

+ */
+message ButlerMetadata {
+	/*
+	 * This enumerates the possible contents of published Butler data.
+	 */
+	enum ContentType {
+		/* The published data is a ButlerLogBundle protobuf message. */
+		ButlerLogBundle = 1;
+	}
+	/* This is the type of data in the subsequent frame. */
+	optional ContentType type = 1;
+
+	/* If true, the content data is compressed. */
+	optional bool compressed = 2;
+}
+
+
+/*
  * A message containing log data in transit from the Butler.
  *
  * The Butler is capable of conserving bandwidth by bundling collected log
@@ -78,12 +98,18 @@ message ButlerLogBundle {
     optional bool terminal = 3;
 
     /*
+     * If terminal is true, this is the terminal stream index; that is, the last
+     * message index in the stream.
+     */
+    optional uint64 terminal_index = 4;
+
+    /*
      * Log entries attached to this record. These must be sequential and in
      * order.
      *
      * This is the main log entry content.
      */
-    repeated protocol.LogEntry logs = 4;
+    repeated protocol.LogEntry logs = 5;
   }
 
   /**