- Electron version: 1.3.3
- Operating system: Windows

I have noticed that a `webview` will emit the `did-navigate-in-page` event when an IFRAME included in the page finishes loading.

Is this the desired behavior? The documentation implies that this event shall only trigger when the main frame's URL hash changes. In any case, a flag `isMainFrame` would be helpful here.

atom/browser/api/atom_api_web_contents.cc
const content::WebContents* web_contents) {
  auto context = web_contents->GetBrowserContext();
  auto site_instance = web_contents->GetSiteInstance();
  if (!context || !site_instance)
    return nullptr;
  auto storage_partition =
      content::BrowserContext::GetStoragePartition(context, site_instance);
  if (!storage_partition)
    return nullptr;
  return storage_partition->GetServiceWorkerContext();
}
void OnCapturePageDone(base::Callback<void(const gfx::Image&)> callback,
                       const SkBitmap& bitmap,
                       content::ReadbackResponse response) {
  callback.Run(gfx::Image::CreateFrom1xBitmap(bitmap));
}
}  
WebContents::WebContents(v8::Isolate* isolate,
                         content::WebContents* web_contents)
    : content::WebContentsObserver(web_contents),
      embedder_(nullptr),
      type_(REMOTE),
      request_id_(0),
      background_throttling_(true) {
  web_contents->SetUserAgentOverride(GetBrowserContext()->GetUserAgent());
  Init(isolate);
  AttachAsUserData(web_contents);
}
WebContents::WebContents(v8::Isolate* isolate,