Worker: Stop calling Isolate::TerminateExecution() on a worker thread

When we need to stop further worker script execution from the worker thread,
we should call WorkerThread::prepareForShutdownOnWorkerThread() that provides
more graceful shutdown sequence than Isolate::TerminateExecution().

BUG=487050

Review-Url: https://codereview.chromium.org/2015823002
Cr-Commit-Position: refs/heads/master@{#396212}
2 files changed