[DevTools] Add WebSocket messages to HAR exports

This patch also enables importing of the newly exported WebSocket
messages

Bug: 496006
Change-Id: I000468d266a570ca46eaa62ac9d7554713896acb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1574606
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Joey Arhar <jarhar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653373}
10 files changed