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This puts into place the intended ownership and starting procedure for
trigger scripts:
- The owner is client_android
- Communication with Java is done with a dedicated bridge

Most of the relevant java <-> native methods are not yet plumbed, this
is done in a downstream CL. Integration tests will be able to provide
coverage for the new code, also further downstream.

Bug: b/171776026
Change-Id: I175fdd1896449575b0a5d944cb2207c588807335
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2524524
Commit-Queue: Clemens Arbesser <arbesser@google.com>
Reviewed-by: Mathias Carlen <mcarlen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#825928}