https://bugs.webkit.org/show_bug.cgi?id=88364

Reviewed by Filip Pizlo.

Source/JavaScriptCore: 

Log GC marking to stderr or a file.  The logging in controlled
with the define ENABLE_OBJECT_MARK_LOGGING in wtf/Platform.h.
If DATA_LOG_TO_FILE in wtf/DataLog.cpp is set to 1, output is
logged to a file otherwise it is logged to stderr.

When logging is enabled, the GC is built single threaded since the
log output from the various threads isn't buffered and output in a
thread safe manner.

* heap/Heap.cpp:
(JSC::Heap::markRoots):
* heap/MarkStack.cpp:
(JSC::MarkStackThreadSharedData::resetChildren):
(JSC::MarkStackThreadSharedData::childVisitCount):
(JSC::MarkStackThreadSharedData::markingThreadMain):
(JSC::MarkStackThreadSharedData::markingThreadStartFunc):
(JSC::MarkStackThreadSharedData::MarkStackThreadSharedData):
(JSC::MarkStackThreadSharedData::reset):
* heap/MarkStack.h:
(MarkStackThreadSharedData):
(MarkStack):
(JSC::MarkStack::sharedData):
(JSC::MarkStack::resetChildCount):
(JSC::MarkStack::childCount):
(JSC::MarkStack::incrementChildCount):
* runtime/JSArray.cpp:
(JSC::JSArray::visitChildren):
* runtime/JSCell.cpp:
(JSC::JSCell::className):
* runtime/JSCell.h:
(JSCell):
(JSC::JSCell::visitChildren):
* runtime/JSString.cpp:
(JSC::JSString::visitChildren):
* runtime/JSString.h:
(JSString):
* runtime/Structure.h:
(JSC::MarkStack::internalAppend):

Source/WTF: 

* wtf/DataLog.cpp:
(WTF::dataLogString): Additional method to support GC Mark logging.
* wtf/DataLog.h:
* wtf/Platform.h: New ENABLE_OBJECT_MARK_LOGGING flag macro.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@119633 268f45cc-cd09-0410-ab3c-d52691b4dbfc