Fix build bot error.

runtime/vm/dart_api_message.cc

Index: runtime/vm/dart_api_message.cc
diff --git a/runtime/vm/dart_api_message.cc b/runtime/vm/dart_api_message.cc
index 0d42246df329f5dfa8da63d5b0a13d915df35067..540434a58aa5eaf58603b33baba8b671b5caa123 100644
--- a/runtime/vm/dart_api_message.cc
+++ b/runtime/vm/dart_api_message.cc
@@ -211,7 +211,7 @@ Dart_CObject* ApiMessageReader::AllocateDartCObjectVmIsolateObj(intptr_t id) {
       Dart_CObject* object = NULL;
       for (intptr_t i = 0; i < vm_isolate_references_.length(); i++) {
         object = vm_isolate_references_.At(i);
-        if ((object->type == Dart_CObject_kString)) {
+        if (object->type == Dart_CObject_kString) {
           if (strcmp(str, const_cast<char*>(object->value.as_string)) == 0) {
             return object;
           }