Defer further starting timeout watch dog.

Defer further starting timeout watch dog.

Recent changed made DOMContentLoaded event to fire before than
Dart application is ready to run.  Therefore the safest bet
timeout watchdog is to wait until the document is fully loaded.

This reverts commit 162f93c5b4def3f2cac2aa1b00fa1d510d1e9940.

Committed: https://code.google.com/p/dart/source/detail?r=1447

[Anton Muhin, 2011-11-10 19:32:25]

All the credits for loaded even go to Vijay!  Thanks a lot, Vijay.

@olonho: Kolya, please, double check that loading request will defer the time
when document will go into "loaded" readyState.

@florian: recently Kolya committed a change which loads necessary dart scripts
directly, and not by appending script tags the document.  This change had an
effect nobody of us foresaw: DOMContentLoaded event now gets triggered before
Dart application is fully loaded.  The former code starts timeout watchdog on
DOMContentLoaded which happily kills the test before it completes.  This change
defers further timeout watchdog start.  Still I am somewhat wildguessing, but at
least locally tests do pass.  I hope when Kolya is over with his investigation,
we'll know for sure if it's ultimate or temporary fix.

[vsm, 2011-11-11 02:33:35]

lgtm

[floitsch, 2011-11-11 07:57:06]

LGTM

[Nikolay, 2011-11-11 12:58:53]

Cool, thanks Anton and Vijay! 
I've checked WebKit, and think approach chosen in CL is correct. 
In Source/WebCore/loader/FrameLoader.cpp function
FrameLoader::checkCompleted() calls 
m_frame->document()->setReadyState(Document::Complete);  
only when
m_frame->document()->cachedResourceLoader()->requestCount() == 0
which means that there are no pending requests, and all scripts are loaded.