Convert ProxyResolvingSocketFactoryRequest to new Mojo types

This CL converts ProxyResolvingSocketFactoryRequest to new Mojo
types using PendingReceiver, Receiver, and UniqueReceiverSet.

Bug: 955171
Change-Id: Ief7194cf589fae12f331ab30f0faeff04efeaefa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1863409
Reviewed-by: Hiroshi Ichikawa <[email protected]>
Reviewed-by: Tommy Nyquist <[email protected]>
Reviewed-by: Maksim Ivanov <[email protected]>
Reviewed-by: Ken Rockot <[email protected]>
Reviewed-by: Kinuko Yasuda <[email protected]>
Reviewed-by: Eugene But <[email protected]>
Reviewed-by: Nicolas Zea <[email protected]>
Reviewed-by: David Roger <[email protected]>
Reviewed-by: Peter Beverloo <[email protected]>
Commit-Queue: Julie Kim <[email protected]>
Cr-Commit-Position: refs/heads/master@{#710275}
42 files changed