Move workers to Chromium threading

Prepare to move workers to Chromium threading

This CL prepares us to move the underlying thread for web workers from a
WTF thread to a Chromium thread. Specifically, this CL removes the notion
of a ThreadID from the WorkerThread interface because that notion doesn't
exist for Chromium threads.

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=150815

[jamesr, 2013-05-20 20:56:28]

lgtm

https://codereview.chromium.org/15338009/diff/3001/Source/core/workers/Worker...
File Source/core/workers/WorkerThread.cpp (left):

https://codereview.chromium.org/15338009/diff/3001/Source/core/workers/Worker...
Source/core/workers/WorkerThread.cpp:181: detachThread(threadID);
hmm, should we make an explicit effort to kill the WebThread here?  When is the
WorkerThread object destructed?  We want to make sure to tear down all WebThread
objects before WebKit::shutdown() is called

[abarth-chromium, 2013-05-20 21:00:36]

https://codereview.chromium.org/15338009/diff/3001/Source/core/workers/Worker...
File Source/core/workers/WorkerThread.cpp (left):

https://codereview.chromium.org/15338009/diff/3001/Source/core/workers/Worker...
Source/core/workers/WorkerThread.cpp:181: detachThread(threadID);
On 2013/05/20 20:56:29, jamesr wrote:
> hmm, should we make an explicit effort to kill the WebThread here?

Yes, I tried for a while having this code release() the WebThread into a local
variable, which ensures that it gets deleted.  The problem is that code below
"m_workerContext = 0" wants to access m_thread.

> When is the WorkerThread object destructed?

It's destructed below "m_workerContext = 0".

> We want to make sure to tear down all WebThread
> objects before WebKit::shutdown() is called

Yes, definitely.

[abarth-chromium, 2013-05-20 22:28:02]

Moving the WorkerMessageLoop over is harder than expected because the code
commonly uses a pattern where it spins a nested run loop and peeks ahead for a
particular message, which it then processes out-of-order.  Sigh.

I'm probably not going to land this CL until I figure that out.

[abarth-chromium, 2013-05-21 17:43:50]

I'm reducing this CL to just removing threadID from the WorkerThread interface. 
I'll change the underlying thread in a later CL.

[commit-bot: I haz the power, 2013-05-21 17:45:56]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/abarth@chromium.org/15338009/9001

[commit-bot: I haz the power, 2013-05-21 19:08:03]

Change committed as 150815