GitLab

Add new feature flag disable_idle_socket_close_on_memory_pressure. If
the flag is turned on, cast_shell won't close idle sockets when memory
pressure happens.

BUG=786585, internal b/73351220, internal b/73495670
TEST=Lauch cast_shell with enable-features=disable_... and watch logs

Change-Id: I5aa22a20103624c3114bc8de34412a9ace0dfa29
Reviewed-on: https://chromium-review.googlesource.com/922902Reviewed-by: Sergey Volk <servolk@chromium.org>
Commit-Queue: Yuchen Liu <yucliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537161}