This test cases ensures that it is possible to maintain a coherent
instruction cache by using {Assembler::FlushICache} in any order with
respect to changing page permissions via {SetPermissions}.

R=ulan@chromium.org
TEST=cctest/test-icache
BUG=v8:6792

Change-Id: I1778bbbe94b40856d9732a9990a931b5a956a439
Reviewed-on: https://chromium-review.googlesource.com/c/1344113Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57651}