* Electron Version: 3.0.0-beta.1 ~ 3.0.0-beta.6
* Operating System (Platform and Version): Ubuntu 16.04.2 LTS
* Last known working Electron version: versions before 3.0.0-beta.1

**Expected Behavior**
Console prints out `time to print stuff` when `Ctrl+P` is pressed.
```
const {Menu, MenuItem} = require('electron')
const menu = new Menu()
  
app.on('ready', () => {
  createWindow()
  menu.append(new MenuItem({
    label: 'Print',
    accelerator: 'CmdOrCtrl+P',
    click: () => { console.log('time to print stuff') }
  }))
  Menu.setApplicationMenu(menu)
})
```
https://github.com/hackjutsu/electron-quick-start/commit/6ceb5d7dcd2d946c071b43a3fdd1b0434ddebff5
**Actual behavior**
No output. The accelerator event is not triggered.

**To Reproduce**
```sh
git clone https://github.com/hackjutsu/electron-quick-start
cd electron-quick-start
npm install
npm run start
```
Try pressing `Ctrl+P`, and observe the output. (nothing happen...)
Change the electron version back to 2.0.0 in `pakcage.json`
```sh
npm install
npm run start
```
Try pressing `Ctrl+P`, and observe the output. (the log `time to print stuff` will show up in console)

atom/browser/ui/views/root_view.cc
#include "atom/browser/ui/views/root_view.h"
#include "atom/browser/native_window.h"
#include "atom/browser/ui/views/menu_bar.h"
#include "content/public/browser/native_web_keyboard_event.h"
namespace atom {
namespace {
#if defined(OS_WIN)
const int kMenuBarHeight = 20;
#else
const int kMenuBarHeight = 25;
#endif
bool IsAltKey(const content::NativeWebKeyboardEvent& event) {
  return event.windows_key_code == ui::VKEY_MENU;
}
bool IsAltModifier(const content::NativeWebKeyboardEvent& event) {
  typedef content::NativeWebKeyboardEvent::Modifiers Modifiers;
  int modifiers = event.GetModifiers();
  modifiers &= ~Modifiers::kNumLockOn;
  modifiers &= ~Modifiers::kCapsLockOn;
  return (modifiers == Modifiers::kAltKey) ||
         (modifiers == (Modifiers::kAltKey | Modifiers::kIsLeft)) ||
         (modifiers == (Modifiers::kAltKey | Modifiers::kIsRight));
}
}  
RootView::RootView(NativeWindow* window)