Remove boostrap sandbox code.

The bootstrap sandbox was replaced by the V2 sandbox.

Bug: 762077
Change-Id: I2c9aeab22d29a42a2c800a53e0c8a5484e00c043
Reviewed-on: https://chromium-review.googlesource.com/647686


Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Commit-Queue: Greg Kerr <kerrnel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501364}