FIXUP: remove typedef for handle map
Web Replay: remove unused NetworkProxy::expectsPageLoad() flag.
Web Replay: add helper function to get a frame's index without its document.
Web Replay: capture network callback inputs from inside SubresourceLoader.

Additionally, don't schedule network requests with NetworkProcess if replaying.
Web Replay: remove ResourceHandle-based capture shim, since it's no longer used.

Closes #405.
Closes #183.