https://bugs.webkit.org/show_bug.cgi?id=84477

Reviewed by Geoffrey Garen.

Currently the Heap cancels the GC timer at the conclusion of a collection. 
We should change this to be at the beginning because something (e.g. a finalizer) 
could call didAbandonObjectGraph(), which will schedule the timer, but then 
we'll immediately unschedule the timer at the conclusion of the collection, 
thus potentially preventing large swaths of memory from being reclaimed in a timely manner.

* API/JSBase.cpp:
(JSGarbageCollect): Remove outdated fix-me and remove check for whether the Heap is 
busy or not, since we're just scheduling a timer to run a GC in the future.
* heap/Heap.cpp:
(JSC::Heap::collect): Rename didCollect to willCollect and move the call to the 
top of Heap::collect.
* runtime/GCActivityCallback.cpp: Renamed didCollect to willCollect.
(JSC::DefaultGCActivityCallback::willCollect):
* runtime/GCActivityCallback.h: Ditto.
(JSC::GCActivityCallback::willCollect):
(DefaultGCActivityCallback): 
* runtime/GCActivityCallbackCF.cpp: Ditto.
(JSC::DefaultGCActivityCallback::willCollect):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@114772 268f45cc-cd09-0410-ab3c-d52691b4dbfc