LogDog: Implement RegisterPrefix RPC.

common/proto/logdog/svcconfig/config.pb.go

Index: common/proto/logdog/svcconfig/config.pb.go
diff --git a/common/proto/logdog/svcconfig/config.pb.go b/common/proto/logdog/svcconfig/config.pb.go
index e8527a43aea65436542c1e082b847595df6b5db1..fd72b39220b1ccc8d79e7d40373ea716130e62bb 100644
--- a/common/proto/logdog/svcconfig/config.pb.go
+++ b/common/proto/logdog/svcconfig/config.pb.go
@@ -104,8 +104,9 @@ type Coordinator struct {
 	// After the expiration period has passed, new log stream registration will
 	// fail.
 	//
-	// Project or stream configurations may override this by providing >= 0 values
-	// for prefix expiration. The smallest configured expiration will be applied.
+	// Project configurations or stream prefix regitrations may override this by
+	// providing >= 0 values for prefix expiration. The smallest configured
+	// expiration will be applied.
 	PrefixExpiration *google_protobuf.Duration `protobuf:"bytes,21,opt,name=prefix_expiration,json=prefixExpiration" json:"prefix_expiration,omitempty"`
 	// The full path of the archival Pub/Sub topic.
 	//