Merge 106636 - Crash when trying to add a timer to a detached document.

Merge 106636 - Crash when trying to add a timer to a detached document.
https://bugs.webkit.org/show_bug.cgi?id=77692

Reviewed by Alexey Proskuryakov.

In http://webkit.org/b/77370, a timer is fired on a detached document.
Since a document clears all timers when it is detached, and it
shouldn't be possible to add a timer to a detached document, we crash
if this should happen anyway. This will hopefully result in an easier
to debug crash dump.

* page/DOMTimer.cpp:
(WebCore::DOMTimer::DOMTimer):


TBR=jochen@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=106682