GetScopedVar should have value profiling

GetScopedVar should have value profiling
https://bugs.webkit.org/show_bug.cgi?id=68676

Reviewed by Oliver Hunt.

Added GetScopedVar value profiling and predictin propagation.
Added GetScopeChain to CSE.

* dfg/DFGByteCodeParser.cpp:
(JSC::DFG::ByteCodeParser::parseBlock):
* dfg/DFGGraph.h:
(JSC::DFG::Graph::predict):
* dfg/DFGNode.h:
(JSC::DFG::Node::hasPrediction):
* dfg/DFGPropagator.cpp:
(JSC::DFG::Propagator::propagateNodePredictions):
(JSC::DFG::Propagator::getScopeChainLoadElimination):
(JSC::DFG::Propagator::performNodeCSE):
* jit/JITPropertyAccess.cpp:
(JSC::JIT::emit_op_get_scoped_var):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@95786 268f45cc-cd09-0410-ab3c-d52691b4dbfc