- Electron version: 1.4.0
- Operating system: OS X 10.10.5

I've been using the following code to send Tab key events to a webview in my project:

``` js
const webContents = webView.getWebContents();
const keyEvent = {
  type: 'keyDown',
  keyCode: 'Tab'
};

webContents.sendInputEvent(keyEvent);
```

I have had no issues with this until the recent update to 1.4.0.

The last version the above code works in OS X is **1.3.7**. I've tried this with the latest versions of Electron (1.4.1 & 1.4.2) with the same results.

Am I doing something wrong here? Is this a known issue?

atom/common/native_mate_converters/blink_converter.cc
v8::Isolate* isolate, v8::Local<v8::Value> val,
    blink::WebDeviceEmulationParams* out) {
  mate::Dictionary dict;
  if (!ConvertFromV8(isolate, val, &dict))
    return false;
  std::string screen_position;
  if (dict.Get("screenPosition", &screen_position)) {
    screen_position = base::ToLowerASCII(screen_position);
    if (screen_position == "mobile")
      out->screenPosition = blink::WebDeviceEmulationParams::Mobile;
    else if (screen_position == "desktop")
      out->screenPosition = blink::WebDeviceEmulationParams::Desktop;
    else
      return false;
  }
  dict.Get("screenSize", &out->screenSize);
  dict.Get("viewPosition", &out->viewPosition);
  dict.Get("deviceScaleFactor", &out->deviceScaleFactor);
  dict.Get("viewSize", &out->viewSize);
  dict.Get("fitToView", &out->fitToView);
  dict.Get("offset", &out->offset);
  dict.Get("scale", &out->scale);
  return true;
}
bool Converter<blink::WebFindOptions>::FromV8(