There's no simple, cross-platform way to register protocol handlers in Electron. Every OS requires a different solution. This seems like something that Electron should smooth over.

There's already a W3C API for this: [`Navigator.registerProtocolHandler`](https://developer.mozilla.org/en-US/docs/Web/API/Navigator/registerProtocolHandler). Can Electron implement it?

atom/browser/browser_win.cc
#include "atom/browser/browser.h"
#include <atlbase.h>
#include <propkey.h>
#include <windows.h>
#include <shlobj.h>
#include <shobjidl.h>
#include "base/base_paths.h"
#include "base/file_version_info.h"
#include "base/files/file_path.h"
#include "base/memory/scoped_ptr.h"
#include "base/path_service.h"
#include "base/strings/string_util.h"
#include "base/strings/stringprintf.h"
#include "base/strings/utf_string_conversions.h"
#include "base/win/win_util.h"
#include "base/win/windows_version.h"
#include "atom/common/atom_version.h"
namespace atom {
namespace {
const wchar_t kAppUserModelIDFormat[] = L"electron.app.$1";
BOOL CALLBACK WindowsEnumerationHandler(HWND hwnd, LPARAM param) {