- Avoid using a streamed receive port for single messages.

runtime/bin/vmservice/loader.dart

Index: runtime/bin/vmservice/loader.dart
diff --git a/runtime/bin/vmservice/loader.dart b/runtime/bin/vmservice/loader.dart
index 2e04455c1546e0135fab432d09bf020022129c3c..ce3c9cce83a79ed14b3f4fb636587e7b78c7466b 100644
--- a/runtime/bin/vmservice/loader.dart
+++ b/runtime/bin/vmservice/loader.dart
@@ -6,7 +6,16 @@ part of vmservice_io;
 
 var _httpClient;
 
-void _loadHttp(sendPort, uri) {
+// Send a response to the requesting isolate.
+void _sendResponse(SendPort sp, int id, dynamic data) {
+  assert((data is List<int>) || (data is String));
+  var msg = new List(2);
+  msg[0] = id;
+  msg[1] = data;
+  sp.send(msg);
+}
+
+void _loadHttp(SendPort sp, int id, Uri uri) {
   if (_httpClient == null) {
     _httpClient = new HttpClient()..maxConnectionsPerHost = 6;
   }
@@ -18,39 +27,41 @@ void _loadHttp(sendPort, uri) {
           builder.add,
           onDone: () {
             if (response.statusCode != 200) {
-              var msg = 'Failure getting $uri: '
-                        '${response.statusCode} ${response.reasonPhrase}';
-              sendPort.send(msg);
+              var msg = "Failure getting $uri:\n"
+                        "  ${response.statusCode} ${response.reasonPhrase}";
+              _sendResponse(sp, id, msg);
             } else {
-              sendPort.send(builder.takeBytes());
+              _sendResponse(sp, id, builder.takeBytes());
             }
           },
           onError: (e) {
-            sendPort.send(e.toString());
+            _sendResponse(sp, d, e.toString());
           });
     })
     .catchError((e) {
-      sendPort.send(e.toString());
+      _sendResponse(sp, id, e.toString());
     });
   // It's just here to push an event on the event loop so that we invoke the
   // scheduled microtasks.
   Timer.run(() {});
 }
 
-void _loadFile(sendPort, path) {
+void _loadFile(SendPort sp, int id, Uri uri) {
+  var path = uri.toFilePath();
   var sourceFile = new File(path);
   sourceFile.readAsBytes().then((data) {
-    sendPort.send(data);
+    _sendResponse(sp, id, data);
   },
   onError: (e) {
-    sendPort.send(e.toString());
+    var err = "Error loading $uri:\n  $e";
+    _sendResponse(sp, id, err);
   });
 }
 
 var dataUriRegex = new RegExp(
     r"data:([\w-]+/[\w-]+)?(;charset=([\w-]+))?(;base64)?,(.*)");
 
-void _loadDataUri(sendPort, uri) {
+void _loadDataUri(SendPort sp, int id, Uri uri) {
   try {
     var match = dataUriRegex.firstMatch(uri.toString());
     if (match == null) throw "Malformed data uri";
@@ -72,21 +83,23 @@ void _loadDataUri(sendPort, uri) {
     }
 
     var data = UTF8.encode(Uri.decodeComponent(encodedData));
-    sendPort.send(data);
+    _sendResponse(sp, id, data);
   } catch (e) {
-    sendPort.send("Invalid data uri ($uri) $e");
+    _sendResponse(sp, id, "Invalid data uri ($uri):\n  $e");
   }
 }
 
 _processLoadRequest(request) {
-  var sp = request[0];
-  var uri = Uri.parse(request[1]);
+  SendPort sp = request[0];
+  int id = request[1];
+  String resource = request[2];
+  var uri = Uri.parse(request[2]);
   if (uri.scheme == 'file') {
-    _loadFile(sp, uri.toFilePath());
+    _loadFile(sp, id, uri);
   } else if ((uri.scheme == 'http') || (uri.scheme == 'https')) {
-    _loadHttp(sp, uri);
+    _loadHttp(sp, id, uri);
   } else if ((uri.scheme == 'data')) {
-    _loadDataUri(sp, uri);
+    _loadDataUri(sp, id, uri);
   } else {
     sp.send('Unknown scheme (${uri.scheme}) for $uri');
   }