* Electron version: 1.7.6
* Operating system: macOS 10.12, Windows 10

### Expected behavior

Right clicking should open context menu in devtools

### Actual behavior

Right clicking does not open the context menu in devtools

### How to reproduce

- `open Electron.app --args --enable-mixed-sandbox`
- open devtools
- right click in the source tab for example
atom/renderer/atom_sandboxed_renderer_client.cc
const base::string16& channel,
                    const base::ListValue& args) {
    if (!frame)
      return;
    auto isolate = blink::MainThreadIsolate();
    v8::HandleScope handle_scope(isolate);
    auto context = frame->MainWorldScriptContext();
    v8::Context::Scope context_scope(context);
    v8::Local<v8::Value> argv[] = {
      mate::ConvertToV8(isolate, channel),
      v8_converter_->ToV8Value(&args, context)
    };
    renderer_client_->InvokeIpcCallback(
        context,
        "onMessage",
        std::vector<v8::Local<v8::Value>>(argv, argv + 2));
  }
 private:
  std::unique_ptr<atom::V8ValueConverter> v8_converter_;
  AtomSandboxedRendererClient* renderer_client_;
  DISALLOW_COPY_AND_ASSIGN(AtomSandboxedRenderFrameObserver);
};
}  
AtomSandboxedRendererClient::AtomSandboxedRendererClient() {
  
  NodeBindings::RegisterBuiltinModules();
}
AtomSandboxedRendererClient::~AtomSandboxedRendererClient() {