Remove usage of dart:json.

sdk/lib/_internal/pub/lib/src/http.dart

Index: sdk/lib/_internal/pub/lib/src/http.dart
diff --git a/sdk/lib/_internal/pub/lib/src/http.dart b/sdk/lib/_internal/pub/lib/src/http.dart
index a54f02f26ae0897790e5f9c5b48788366c4709ad..9fc338eb031e87c337d6da87579891244e7fb257 100644
--- a/sdk/lib/_internal/pub/lib/src/http.dart
+++ b/sdk/lib/_internal/pub/lib/src/http.dart
@@ -6,8 +6,8 @@
 library pub.http;
 
 import 'dart:async';
+import 'dart:convert';
 import 'dart:io';
-import 'dart:json' as json;
 
 import 'package:http/http.dart' as http;
 
@@ -203,7 +203,7 @@ void handleJsonError(http.Response response) {
 Map parseJsonResponse(http.Response response) {
   var value;
   try {
-    value = json.parse(response.body);
+    value = JSON.decode(response.body);
   } on FormatException catch (e) {
     invalidServerResponse(response);
   }