[Compiler] Avoid flaky crashes for aborted compiler dispatcher jobs.

Make sure we wait for the worker thread to finish compilation before removing
aborted jobs.

BUG=v8:8317,v8:8041

Change-Id: I42f30c4d430b7787ea5e724bdfda6460e5461233
Reviewed-on: https://chromium-review.googlesource.com/c/1288812Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56787}

src/compiler-dispatcher/compiler-dispatcher.h

@@ -122,7 +122,7 @@ class V8_EXPORT_PRIVATE CompilerDispatcher {
     ~Job();
 
     bool IsReadyToFinalize(const base::MutexGuard&) {
-      return aborted || (has_run && !function.is_null());
+      return has_run && (!function.is_null() || aborted);
     }
 
     bool IsReadyToFinalize(base::Mutex* mutex) {