... and don't clear ICs during GC. The IC clearing used to prevent memory
leaks but it's not necessary anymore because all the handlers that need
to embed objects already use weak cells.

This CL unblocks inlining of IC dispatchers into bytecode handlers.

BUG=v8:5917

Change-Id: I229b9ba8dba44f431dfbe8ac5370d855e3e84dd6
Reviewed-on: https://chromium-review.googlesource.com/442127
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43209}