[turbofan] Turn JSToBoolean and JSUnaryNot into pure operators.

src/compiler/js-graph.h

Index: src/compiler/js-graph.h
diff --git a/src/compiler/js-graph.h b/src/compiler/js-graph.h
index 9d496d53c952e6230139380e10d52ae7de97d18a..064359423fb5f2f6e032f0b182bb7cd9c0deca96 100644
--- a/src/compiler/js-graph.h
+++ b/src/compiler/js-graph.h
@@ -105,6 +105,10 @@ class JSGraph : public ZoneObject {
     return Constant(immediate);
   }
 
+  // Creates a dummy Constant node, used to satisfy calling conventions of
+  // stubs and runtime functions that do not require a context.
+  Node* NoContextConstant() { return ZeroConstant(); }
+
   JSOperatorBuilder* javascript() { return javascript_; }
   CommonOperatorBuilder* common() { return common_; }
   MachineOperatorBuilder* machine() { return machine_; }