This is more consistent with the DOM API, and is clearer w.r.t. which values
are available in the lexical environment of the Worker.
BUG=chromium:497295
R=jarin@chromium.org
LOG=n
Review URL: https://codereview.chromium.org/1218553004
Cr-Commit-Position: refs/heads/master@{#29426}
The issue is that Worker.prototype.terminate was deleting the C++ Worker
object, and then Worker.prototype.getMessage was trying to read messages from
the queue.
The simplest solution is to keep workers in a zombie state when they have been
terminated. They won't be reaped until Shell::CleanupWorkers is called.
I've also fixed some threading issues with Workers:
* Workers can be created by another Worker, so the Shell::workers_ variable
must be protected by a mutex.
* An individual Worker can typically only be accessed by the isolate that
created it, but the main thread can always terminate it, so the Worker::state_
must be accessed in a thread-safe way.
BUG=chromium:504136
R=jochen@chromium.org
LOG=n
Review URL: https://codereview.chromium.org/1208733002
Cr-Commit-Position: refs/heads/master@{#29306}
