* Electron version: 1.8.2
* Operating system: macos 10.13.3

Reproducing repo: https://github.com/ibash/electron-webkit-app-drag

Demonstrates a bug where `-webkit-app-region: drag` causes a browser view in front of it to miss click events. Oddly - it does not prevent hover events.

Steps:
1. Clone https://github.com/ibash/electron-webkit-app-drag, `yarn install`, `yarn start`
2. Click "button1"
3. Click "button2"

Expected:

Clicking button1 or button2 pops up an alert: "button clicked!"

Actual:

Only clicking button2 pops up an alert: "button clicked!"

atom/browser/api/atom_api_browser_window.cc
double offsetX = 0.0;
  args->GetNext(&offsetX);
  window_->SetSheetOffset(offsetX, offsetY);
}
void BrowserWindow::SetResizable(bool resizable) {
  window_->SetResizable(resizable);
}
bool BrowserWindow::IsResizable() {
  return window_->IsResizable();
}
void BrowserWindow::SetMovable(bool movable) {
  window_->SetMovable(movable);
}
bool BrowserWindow::IsMovable() {
  return window_->IsMovable();
}
void BrowserWindow::SetMinimizable(bool minimizable) {
  window_->SetMinimizable(minimizable);
}
bool BrowserWindow::IsMinimizable() {
  return window_->IsMinimizable();
}
void BrowserWindow::SetMaximizable(bool maximizable) {
  window_->SetMaximizable(maximizable);
}
bool BrowserWindow::IsMaximizable() {