Improve Hydrogen code for accessing undefined/null/Infinity.

src/factory.cc

Index: src/factory.cc
===================================================================
--- src/factory.cc	(revision 9408)
+++ src/factory.cc	(working copy)
@@ -1315,4 +1315,13 @@
 }
 
 
+Handle<Object> Factory::GlobalConstantFor(Handle<String> name) {
+  Heap* h = isolate()->heap();
+  if (name->Equals(h->undefined_symbol())) return undefined_value();
+  if (name->Equals(h->nan_symbol())) return nan_value();
+  if (name->Equals(h->infinity_symbol())) return infinity_value();
+  return Handle<Object>::null();
+}
+
+
 } }  // namespace v8::internal