All compile tasks are already canceled when the {CompilationState}
dies. This happens when the {NativeModule} dies, and all
{NativeModule}s die before the {WasmEngine} dies. Thus, the WasmEngine
does not need to cancel any compile jobs, because there are none anyway.

R=mstarzinger@chromium.org

Bug: chromium:869420
Change-Id: I7e006392a1f9126333733c81c4c19985f626a470
Reviewed-on: https://chromium-review.googlesource.com/1158411Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54840}