[DevTools] Check net::LoadTimingInfo in NetworkHandler

This patch checks net::LoadTimingInfo for an invalid value indicating
that the net::LoadTimingInfo is not valid and should not be present in
responseReceived. The check for receive_header_end in particular is the
same as the one we are already doing in the renderer in
WebURLLoaderImpl::PopulateURLResponse:
https://cs.chromium.org/chromium/src/content/renderer/loader/web_url_loader_impl.cc?l=1132-1141&rcl=0e067b8d07e4fa74c1bc0982b5cdc5c490674311

Bug: 935247
Change-Id: I654d3d407be12a061022a64967f164e1d050ac78
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1650532
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Commit-Queue: Joey Arhar <jarhar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#667800}