* 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
base::CommandLine* command_line,
    int process_id) {
  
  {
    base::FilePath child_path;
    base::PathService::Get(content::CHILD_PROCESS_EXE, &child_path);
    base::ThreadRestrictions::ScopedAllowIO allow_io;
    CHECK(base::MakeAbsoluteFilePath(command_line->GetProgram()) == child_path);
  }
  std::string process_type =
      command_line->GetSwitchValueASCII(::switches::kProcessType);
  if (process_type != ::switches::kRendererProcess)
    return;
  
  static const char* const kCommonSwitchNames[] = {
      switches::kStandardSchemes,     switches::kEnableSandbox,
      switches::kSecureSchemes,       switches::kBypassCSPSchemes,
      switches::kCORSSchemes,         switches::kFetchSchemes,
      switches::kServiceWorkerSchemes};
  command_line->CopySwitchesFrom(*base::CommandLine::ForCurrentProcess(),
                                 kCommonSwitchNames,
                                 arraysize(kCommonSwitchNames));
#if defined(OS_WIN)