Embedding arbitrary web content is problematic when it comes to keyboard shortcuts because:
- Web content can steal app shortcuts (see e.g. brave/browser-laptop#4407)
- Blocked web content (e.g. a focused `<webview>` performing expensive computation) will also prevent app shortcuts from firing immediately

To fix this, we need a way to _always_ handle certain shortcuts in the main process. I think the most flexible solution would be something like this:

``` js
app.addProtectedShortcut('CmdOrCtrl+Tab', (event) => {
  event.preventDefault();
});
```

We could then implement:

``` cpp
bool CommonWebContentsDelegate::PreHandleKeyboardEvent(
    content::WebContents* source,
    const content::NativeWebKeyboardEvent& event,
    bool* is_keyboard_shortcut) {
  return /* event is protected shortcut and the handler called preventDefault */;
}
```

@zcbenz Thoughts? I'm happy to work on this if we come up with a reasonable approach.

atom/browser/api/atom_api_web_contents.cc
rect.size();
  
  
  
  gfx::Size bitmap_size = view_size;
  const gfx::NativeView native_view = view->GetNativeView();
  const float scale =
      display::Screen::GetScreen()->GetDisplayNearestWindow(native_view)
      .device_scale_factor();
  if (scale > 1.0f)
    bitmap_size = gfx::ScaleToCeiledSize(view_size, scale);
  host->CopyFromBackingStore(gfx::Rect(rect.origin(), view_size),
                             bitmap_size,
                             base::Bind(&OnCapturePageDone, callback),
                             kBGRA_8888_SkColorType);
}
void WebContents::OnCursorChange(const content::WebCursor& cursor) {
  content::WebCursor::CursorInfo info;
  cursor.GetCursorInfo(&info);
  if (cursor.IsCustom()) {
    Emit("cursor-changed", CursorTypeToString(info),
      gfx::Image::CreateFrom1xBitmap(info.custom_image),
      info.image_scale_factor,
      gfx::Size(info.custom_image.width(), info.custom_image.height()),
      info.hotspot);
  } else {
    Emit("cursor-changed", CursorTypeToString(info));
  }
}
void WebContents::SetSize(const SetSizeParams& params) {