Rewrite LogDog log viewer app.

web/inc/logdog-stream/logdog-error.html

 <!--
   Copyright 2016 The LUCI Authors. All rights reserved.
   Use of this source code is governed under the Apache License, Version 2.0
   that can be found in the LICENSE file.
   -->
 
 <link rel="import" href="../rpc/rpc-error.html">
 
 <script>
   "use strict";
 
   function LogDogError(base) {
     this.base = base;
   };
   LogDogError.wrapGrpc = function(err) {
     if (err instanceof luci.rpc.GrpcError) {
       return new LogDogError(err);
     }
     return err;
   }
 
   LogDogError.prototype = Object.create(Error.prototype);
   LogDogError.prototype.isGrpcError = function() {
     return (this.base.name === "GrpcError");
   };
   LogDogError.prototype.isNotFound = function() {
-    return (this.isGrpcError() && this.base.code === 5);
+    return (this.isGrpcError() && this.base.code === luci.rpc.Code.NOT_FOUND);
   };
   LogDogError.prototype.isUnauthenticated = function() {
-    return (this.isGrpcError() && this.base.code === 16);
+    return (this.isGrpcError() &&
+        this.base.code === luci.rpc.Code.UNAUTHENTICATED);
+  };
+  LogDogError.prototype.isTransient = function() {
+    if ( ! this.isGrpcError() ) {
+      return false;
+    }
+    switch ( this.base.code ) {
+    case luci.rpc.Code.INTERNAL:
+    case luci.rpc.Code.UNAVAILABLE:
+    case luci.rpc.Code.RESOURCE_EXHAUSTED:
+      return true;
+
+    default:
+      return false;
+    }
   };
 </script>