Evacuating and compacting LayoutDescriptor is meta-circular, i.e., we
need the descriptor to iterate the objects that are copied. Separate the
phases to avoid requiring a publishing store for object payloads.

This reverts commit 6f4a86c1.

CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel;master.tryserver.chromium.android:android_optional_gpu_tests_rel

Bug: v8:6884
Change-Id: I71472eaf7671ede20ff4b19f1f0c9490cdb0b629
Reviewed-on: https://chromium-review.googlesource.com/702255Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48307}