Buildbot build json grpc endpoint

milo/api/proto/buildbot.proto

Index: milo/api/proto/buildbot.proto
diff --git a/milo/api/proto/buildbot.proto b/milo/api/proto/buildbot.proto
index 04192de08f292a88661e6fa5ccdd10f161cc918c..e8a038fa2f83dacb33398ae2c25a7cb0cd4c8021 100644
--- a/milo/api/proto/buildbot.proto
+++ b/milo/api/proto/buildbot.proto
@@ -11,6 +11,7 @@ import "google/protobuf/timestamp.proto";
 // The buildbot service definition.
 service Buildbot {
   rpc GetCompressedMasterJSON(MasterRequest) returns (CompressedMasterJSON) {}
+  rpc GetBuildbotBuildJSON(BuildbotBuildRequest) returns (BuildbotBuildJSON) {}
 }
 
 // The request containing the name of the master.
@@ -29,3 +30,16 @@ message CompressedMasterJSON {
   // Gzipped json data of the master.
   bytes data = 3;
 }
+
+// The request for a specific build.
+message BuildbotBuildRequest {
+  string master = 1;
+  string builder = 2;
+  int64 build_num = 3;
+}
+
+// The response message for a specific build.
+message BuildbotBuildJSON {
+  // Json data of the build.
+  bytes data = 1;
+}