- Introduce native/ and osr/ folders for native (non-platform-agnostic) and
osr (windowless) code respectively.
- Introduce CefBrowserPlatformDelegate for abstracting platform-specific
implementations of browser host functionality.
- Move dialog and menu code to separate manager and platform-specific runner
implementations exposed via CefBrowserPlatformDelegate.
- Standardize focus-handling behavior between windowed and windowless
implementations. CefFocusHandler::OnSetFocus() will now also be called for
osr focus changes.
- Support multiple simultaneous popups (issue #1289).
