Don't pass --harmony-promises flag from gin to v8

gin/isolate_holder.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "gin/public/isolate_holder.h"
 
 #include <stdlib.h>
 #include <string.h>
 
 #include "base/logging.h"
@@ skipping 22 matching lines @@
     return;
   }
   v8_is_initialized = true;
   v8_is_gin_managed = gin_managed;
   if (!gin_managed)
     return;
 
   v8::V8::InitializePlatform(V8Platform::Get());
   v8::V8::SetArrayBufferAllocator(ArrayBufferAllocator::SharedInstance());
   if (mode == gin::IsolateHolder::kStrictMode) {
-    static const char v8_flags[] = "--use_strict --harmony_promises";
+    static const char v8_flags[] = "--use_strict";
     v8::V8::SetFlagsFromString(v8_flags, sizeof(v8_flags) - 1);
   }
   v8::V8::SetEntropySource(&GenerateEntropy);
   v8::V8::Initialize();
 }
 
 }  // namespace
 
 IsolateHolder::IsolateHolder(ScriptMode mode)
   : isolate_owner_(true) {
@@ skipping 20 matching lines @@
     isolate_->Dispose();
 }
 
 void IsolateHolder::Init(v8::ArrayBuffer::Allocator* allocator) {
   v8::Isolate::Scope isolate_scope(isolate_);
   v8::HandleScope handle_scope(isolate_);
   isolate_data_.reset(new PerIsolateData(isolate_, allocator));
 }
 
 }  // namespace gin