Previously explicit calls to external memory adjustment could yield in lowering
the limit below the initial default limit. The consequence is repeated useless
garbage collections when e.g. passing around ArrayBuffers.

Bug: chromium:880036
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I429f5adcd9ae523e5ac7621cf7976686b0dec71b
Reviewed-on: https://chromium-review.googlesource.com/1209784Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55694}