LogDog: Implement RegisterPrefix RPC.

appengine/logdog/coordinator/logPrefix.go

Index: appengine/logdog/coordinator/logPrefix.go
diff --git a/appengine/logdog/coordinator/logPrefix.go b/appengine/logdog/coordinator/logPrefix.go
index 9571d00ae8e5a65315f51160ce17cf3f8ad05c6a..4618688acb6608e47d5c263dbdc2eff698fed807 100644
--- a/appengine/logdog/coordinator/logPrefix.go
+++ b/appengine/logdog/coordinator/logPrefix.go
@@ -32,14 +32,17 @@ type LogPrefix struct {
 	Schema string
 
 	// Created is the time when this stream was created.
-	Created time.Time
+	Created time.Time `gae:",noindex"`
 
 	// Prefix is this log stream's prefix value. Log streams with the same prefix
 	// are logically grouped.
 	//
 	// This value should not be changed once populated, as it will invalidate the
 	// HashID.
-	Prefix string
+	Prefix string `gae:",noindex"`
+
+	// Source is the (indexed) set of source strings sent by the prefix registrar.
+	Source []string
 
 	// Secret is the Butler secret value for this prefix. All streams within
 	// the prefix share this secret value.