Revert of Fix SharedWorker leak when script load has failed.

Revert of Fix SharedWorker leak when script load has failed. (https://codereview.chromium.org/424653002/)

Reason for revert:
May cause crash

Original issue's description:
> Fix SharedWorker leak when script load has failed.
> 
> When SharedWorker script load has failed and the |WebSharedWorkerImpl|
> was explicit told to terminate, the |WebSharedWorkerImpl| instance
> was never deleted.
> 
> This CL fixes the issue by invoking "delete this" when a worker thread
> instance does not exist in |stopWorkerThread()|.
> 
> TEST=fast/workers/worker-crash-with-invalid-location.html doesn't leak when --enable-leak-detection
> BUG=364390
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=179011

TBR=falken@chromium.org,tkent@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=364390
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=179088

[kouhei (in TOK), 2014-07-29 02:31:39]

Created Revert of Fix SharedWorker leak when script load has failed.

[commit-bot: I haz the power, 2014-07-29 02:32:05]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/kouhei@chromium.org/424923002/1

[commit-bot: I haz the power, 2014-07-29 02:33:32]

Change committed as 179088

[tkent, 2014-07-29 02:36:58]

lgtm