LogDog: Implement RegisterPrefix RPC.

common/proto/logdog/svcconfig/config.proto

Index: common/proto/logdog/svcconfig/config.proto
diff --git a/common/proto/logdog/svcconfig/config.proto b/common/proto/logdog/svcconfig/config.proto
index 721524d47e541762fd4b0fc47f0f73c3721bdb3d..0c611f0f9e682ff39ac39af521e6cc272bdea31d 100644
--- a/common/proto/logdog/svcconfig/config.proto
+++ b/common/proto/logdog/svcconfig/config.proto
@@ -39,6 +39,16 @@ message Coordinator {
   // A list of origin URLs that are allowed to perform CORS RPC calls.
   repeated string rpc_allow_origins = 20;
 
+  // The maximum amount of time after a prefix has been registered when log
+  // streams may also be registered under that prefix.
+  //
+  // After the expiration period has passed, new log stream registration will
+  // fail.
+  //
+  // Project or stream configurations may override this by providing >= 0 values

[nodir, 2016/05/17 02:45:59]

s/stream/prefix/?

[dnj (Google), 2016/05/17 14:44:33]

Done.

+  // for prefix expiration. The smallest configured expiration will be applied.
+  google.protobuf.Duration prefix_expiration = 21;
+
   // The full path of the archival Pub/Sub topic.
   //
   // The Coordinator must have permission to publish to this topic.