We currently store the protected instructions per code object in a
{std::unique_ptr<std::vector<ProtectedInstructionData>>}. This wastes
memory, because it requires two heap allocations, plus the vector might
over-allocate (and it currently does, because it is filled dynamically
during compilation).
This CL changes that to store the protected instructions in an
{OwnedVector}. This requires one copy after generating the list of
{ProtectedInstructionData} in an {std::vector} during compilation, but
saves memory afterwards.

R=mstarzinger@chromium.org

Bug: chromium:856938
Change-Id: Ie290a17dc32f27fbbfe0c000a52297181c954550
Reviewed-on: https://chromium-review.googlesource.com/1116701Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54052}