- Electron version: 1.2.8
- Operating system: Windows

Hi,

I've been trying to get a context menu containing some [predefined web contents roles](https://github.com/electron/electron/blob/master/lib/browser/api/menu-item-roles.js#L17) working for an application where we have multiple windows simultaneously. I've noticed that when a context menu is opened for a window that was created later than others, the role commands don't seem to execute when clicked. However, if don't use a role and instead define a click handler that calls the command on the web contents manually, it behaves normally.

I've been doing some digging and it seems that the reason is because, for a role, [`electron.webContents.getFocusedWebContents`](https://github.com/electron/electron/blob/master/lib/browser/api/web-contents.js#L257) is used to determine which web contents to call the command on (see [menu.js](https://github.com/electron/electron/blob/master/lib/browser/api/menu.js#L121)).

This function iterates through all existing web contents, then returns the first in the collection that is in a `webview`, otherwise the first that returns `true` from `contents.isFocused()`. However, it seems to be entirely possible that there are web contents other than the one that the context menu was raised for, who think they are focused (or perhaps are within a `webview`), and who were created earlier and therefore appear earlier in the collection.

This means there are situations when the 'wrong' web contents is returned from `getFocusedWebContents`, and therefore the role command is called on that 'wrong' web contents, which leads to the unexpected behaviour described above.

Is this a bug? And if so, is there a fix and/or workaround for this? I'm happy to contribute a PR if needed.

atom/browser/api/atom_api_web_contents.cc
v8::Isolate* isolate, content::WebContents* web_contents) {
  
  auto existing = TrackableObject::FromWrappedClass(isolate, web_contents);
  if (existing)
    return mate::CreateHandle(isolate, static_cast<WebContents*>(existing));
  
  return mate::CreateHandle(isolate, new WebContents(isolate, web_contents));
}
mate::Handle<WebContents> WebContents::Create(
    v8::Isolate* isolate, const mate::Dictionary& options) {
  return mate::CreateHandle(isolate, new WebContents(isolate, options));
}
}  
}  
namespace {
using atom::api::WebContents;
void Initialize(v8::Local<v8::Object> exports, v8::Local<v8::Value> unused,
                v8::Local<v8::Context> context, void* priv) {
  v8::Isolate* isolate = context->GetIsolate();
  mate::Dictionary dict(isolate, exports);
  dict.Set("WebContents", WebContents::GetConstructor(isolate)->GetFunction());
  dict.SetMethod("create", &WebContents::Create);
  dict.SetMethod("fromId", &mate::TrackableObject<WebContents>::FromWeakMapID);
  dict.SetMethod("getAllWebContents",
                 &mate::TrackableObject<WebContents>::GetAll);
}
}  
NODE_MODULE_CONTEXT_AWARE_BUILTIN(atom_browser_web_contents, Initialize)