Clear request body on redirect if new method is GET in webRequest proxy

This is similar to what is done in CorsURLLoader:
https://cs.chromium.org/chromium/src/services/network/cors/cors_url_loader.cc?l=138&rcl=cc2c755f47023edd66e89d836e467e505d124320

Bug: 923622
Change-Id: I26e15c250b08a0fa0c1f6fcdd1ceb21b776cae89
Reviewed-on: https://chromium-review.googlesource.com/c/1423919
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Commit-Queue: Clark DuVall <cduvall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#624454}
1 file changed