Speech JavaScript API: Don't dispatch end event after ActiveDOMObject::stop()

Speech JavaScript API: Don't dispatch end event after ActiveDOMObject::stop()
https://bugs.webkit.org/show_bug.cgi?id=90176

Reviewed by Adam Barth.

Source/WebCore:

It is probably not safe to dispatch an event on an object that has
been ActiveDOMObject::stop()'ed.

This used to happen in the navigate-away.html test, which I believe
then caused speechgrammar-basics.html (which was typically run
afterwards, by the same worker), to crash flakily. See Bug 89717.

Test: speechgrammar-basics.html should no longer be flaky.

* Modules/speech/SpeechRecognition.cpp:
(WebCore::SpeechRecognition::didEnd):
(WebCore::SpeechRecognition::stop):
(WebCore::SpeechRecognition::SpeechRecognition):
* Modules/speech/SpeechRecognition.h:

LayoutTests:

speechgrammar-basics.html should no longer be flaky.

* platform/chromium/TestExpectations:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@121438 268f45cc-cd09-0410-ab3c-d52691b4dbfc