* Output of `node_modules/.bin/electron --version`: v5.0.0-nightly.20190107
* Operating System (Platform and Version): macOS Mojave 10.14.2 (18C54)
* Output of `node_modules/.bin/electron --version` on last known working Electron version (if applicable): never

**Expected Behavior**
Using navigator.mediaDevices.getDisplayMedia({ video: true }), a native screen picker should appear.

**Actual behavior**
The following error is thrown: NotAllowedError: Permission denied

**Screenshots**
Expected dialog
![image](https://user-images.githubusercontent.com/1120050/51625551-71736500-1f0b-11e9-9a95-1406cad95046.png)
atom/browser/atom_browser_client.cc
content::RenderFrameHost* current_rfh,
    content::RenderFrameHost* speculative_rfh,
    content::BrowserContext* browser_context,
    const GURL& url,
    bool has_response_started) const {
  if (url.SchemeIs(url::kJavaScriptScheme))
    
    return false;
  content::SiteInstance* current_instance = current_rfh->GetSiteInstance();
  content::SiteInstance* speculative_instance =
      speculative_rfh ? speculative_rfh->GetSiteInstance() : nullptr;
  int process_id = current_instance->GetProcess()->GetID();
  if (NavigationWasRedirectedCrossSite(browser_context, current_instance,
                                       speculative_instance, url,
                                       has_response_started)) {
    
    
    return false;
  } else if (IsRendererSandboxed(process_id)) {
    
    
    return false;
  } else if (!RendererUsesNativeWindowOpen(process_id)) {
    
    
    return true;
  } else {
    auto* web_contents = content::WebContents::FromRenderFrameHost(current_rfh);
    if (!ChildWebContentsTracker::FromWebContents(web_contents)) {