Improve --trace-service to help track down problems in full_coverage_test.

runtime/lib/developer.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:isolate';
 
 patch bool debugger({bool when: true,
                      String message}) native "Developer_debugger";
 
 patch Object inspect(Object object) native "Developer_inspect";
@@ skipping 49 matching lines @@
 
 patch _registerExtension(String method, ServiceExtensionHandler handler)
     native "Developer_registerExtension";
 
 // This code is only invoked when there is no other Dart code on the stack.
 _runExtension(ServiceExtensionHandler handler,
               String method,
               List<String> parameterKeys,
               List<String> parameterValues,
               SendPort replyPort,
-              Object id) {
+              Object id,
+              bool trace_service) {
   var parameters = {};
   for (var i = 0; i < parameterKeys.length; i++) {
     parameters[parameterKeys[i]] = parameterValues[i];
   }
   var response;
   try {
     response = handler(method, parameters);
   } catch (e, st) {
     var errorDetails = (st == null) ? '$e' : '$e\n$st';
     response = new ServiceExtensionResponse.error(
         ServiceExtensionResponse.kExtensionError,
         errorDetails);
-    _postResponse(replyPort, id, response);
+    _postResponse(replyPort, id, response, trace_service);
     return;
   }
   if (response is! Future) {
     response = new ServiceExtensionResponse.error(
           ServiceExtensionResponse.kExtensionError,
           "Extension handler must return a Future");
-    _postResponse(replyPort, id, response);
+    _postResponse(replyPort, id, response, trace_service);
     return;
   }
   response.catchError((e, st) {
     // Catch any errors eagerly and wrap them in a ServiceExtensionResponse.
     var errorDetails = (st == null) ? '$e' : '$e\n$st';
     return new ServiceExtensionResponse.error(
         ServiceExtensionResponse.kExtensionError,
         errorDetails);
   }).then((response) {
     // Post the valid response or the wrapped error after verifying that
     // the response is a ServiceExtensionResponse.
     if (response is! ServiceExtensionResponse) {
       response = new ServiceExtensionResponse.error(
           ServiceExtensionResponse.kExtensionError,
           "Extension handler must complete to a ServiceExtensionResponse");
     }
-    _postResponse(replyPort, id, response);
+    _postResponse(replyPort, id, response, trace_service);
   }).catchError((e, st) {
     // We do not expect any errors to occur in the .then or .catchError blocks
     // but, suppress them just in case.
   });
 }
 
 // This code is only invoked by _runExtension.
 _postResponse(SendPort replyPort,
               Object id,
-              ServiceExtensionResponse response) {
+              ServiceExtensionResponse response,
+              bool trace_service) {
   assert(replyPort != null);
   if (id == null) {
+    if (trace_service) {
+      print("vm-service: posting no response for request");
+    }
     // No id -> no response.
     replyPort.send(null);
     return;
   }
   assert(id != null);
   StringBuffer sb = new StringBuffer();
   sb.write('{"jsonrpc":"2.0",');
   if (response._isError()) {
+    if (trace_service) {
+      print("vm-service: posting error response for request $id");
+    }
     sb.write('"error":');
   } else {
+    if (trace_service) {
+      print("vm-service: posting response for request $id");
+    }
     sb.write('"result":');
   }
   sb.write('${response._toString()},');
   if (id is String) {
     sb.write('"id":"$id"}');
   } else {
     sb.write('"id":$id}');
   }
   replyPort.send(sb.toString());
 }