Update return type of dart2js patch of dart:developer.log.

runtime/lib/developer.dart

Index: runtime/lib/developer.dart
diff --git a/runtime/lib/developer.dart b/runtime/lib/developer.dart
index 707d59144808c8bbe034a3836c43c4a1f6835c74..3fa9bffa237b91788a0a31b2f9db44dba798aadb 100644
--- a/runtime/lib/developer.dart
+++ b/runtime/lib/developer.dart
@@ -7,14 +7,14 @@ patch bool debugger({bool when: true,
 
 patch Object inspect(Object object) native "Developer_inspect";
 
-patch log(String message,
-          {DateTime time,
-           int sequenceNumber,
-           int level: 0,
-           String name: '',
-           Zone zone,
-           Object error,
-           StackTrace stackTrace}) {
+patch void log(String message,
+               {DateTime time,
+                int sequenceNumber,
+                int level: 0,
+                String name: '',
+                Zone zone,
+                Object error,
+                StackTrace stackTrace}) {
   if (message is! String) {
     throw new ArgumentError(message, "message", "Must be a String");
   }