* Electron version: 1.7.x
* Operating system: Windows

### Expected behavior
removeAsDefaultProtocolClient should also delete the protocol key - HKCU\Software\Classes\#protocol#

### Actual behavior
removeAsDefaultProtocolClient doesn't delete the protocol key - HKCU\Software\Classes\#protocol#

### How to reproduce
Call app.setAsDefaultProtocolClient('foo') and app.removeAsDefaultProtocolClient('foo'). HKCU\Software\Classes\foo stay in the registry for windows.
atom/browser/browser_win.cc
const std::vector<base::string16>& launch_args) {
  if (exe->empty() && !GetProcessExecPath(exe)) {
    return false;
  }
  if (!launch_args.empty()) {
    *exe = base::StringPrintf(L"%ls %ls",
                              exe->c_str(),
                              base::JoinString(launch_args, L" ").c_str());
  }
  return true;
}
}  
void Browser::Focus() {
  
  DWORD pid = GetCurrentProcessId();
  EnumWindows(&WindowsEnumerationHandler, reinterpret_cast<LPARAM>(&pid));
}
void Browser::AddRecentDocument(const base::FilePath& path) {