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This commit replaces the original pywebsocket with pywebsocket3 on //net
tests, and removes any deprecated features. This also tweaks some of the
websocket handlers that used the old API to use new ones.

Change-Id: I6b77d0ed524c3ff279aa659b2ca6c4048e5da95e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2054125Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: David Benjamin <davidben@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Adam Rice <ricea@chromium.org>
Commit-Queue: Keita Suzuki <suzukikeita@google.com>
Cr-Commit-Position: refs/heads/master@{#747618}