* Output of `node_modules/.bin/electron --version`: 2.0.0
* Operating System (Platform and Version): Windows 10

**Expected Behavior**
When I disable a window twice via `setEnabled(false)`, I expect the second disable to have no effect.

**Actual behavior**
The second disable is "queued" up, such that I am forced to enable the window twice to get back to normal.

**To Reproduce**
In the electronquickstart repo, in main.js' `createWindow()`, add these lines:

    mainWindow.setEnabled(false);
    mainWindow.setEnabled(false);
    mainWindow.setEnabled(true);

The window will be disabled when launched. 

You see the same issue if you do it in reverse:

    mainWindow.setEnabled(true);
    mainWindow.setEnabled(false); // this doesn't actually disable it, because the window was enabled from the getgo

If this is expected behavior, can the [docs](https://github.com/electron/electron/blob/master/docs/api/browser-window.md#winsetenabledenable) be updated to explain this behavior.
atom/browser/native_window_views.cc
#if defined(OS_WIN)
  FlipWindowStyle(GetAcceleratedWidget(), maximizable, WS_MAXIMIZEBOX);
#endif
  maximizable_ = maximizable;
}
bool NativeWindowViews::IsMaximizable() {
#if defined(OS_WIN)
  return ::GetWindowLong(GetAcceleratedWidget(), GWL_STYLE) & WS_MAXIMIZEBOX;
#else
  return true;  
#endif
}
void NativeWindowViews::SetFullScreenable(bool fullscreenable) {
  fullscreenable_ = fullscreenable;
}
bool NativeWindowViews::IsFullScreenable() {
  return fullscreenable_;
}
void NativeWindowViews::SetClosable(bool closable) {
#if defined(OS_WIN)
  HMENU menu = GetSystemMenu(GetAcceleratedWidget(), false);
  if (closable) {
    EnableMenuItem(menu, SC_CLOSE, MF_BYCOMMAND | MF_ENABLED);
  } else {
    EnableMenuItem(menu, SC_CLOSE, MF_BYCOMMAND | MF_DISABLED | MF_GRAYED);
  }
#endif
}
bool NativeWindowViews::IsClosable() {