Revert "Use an explicit 'this' parameter instead of 'This' nodes."

pkg/compiler/lib/src/cps_ir/type_propagation.dart

Index: pkg/compiler/lib/src/cps_ir/type_propagation.dart
diff --git a/pkg/compiler/lib/src/cps_ir/type_propagation.dart b/pkg/compiler/lib/src/cps_ir/type_propagation.dart
index bd723fc1f0a17f132dcec9f080823ff8acec9239..bdacd015367b857e01c2152b372cbf76ea9f7d32 100644
--- a/pkg/compiler/lib/src/cps_ir/type_propagation.dart
+++ b/pkg/compiler/lib/src/cps_ir/type_propagation.dart
@@ -422,9 +422,6 @@ class _TypePropagationVisitor<T> implements Visitor {
   }
 
   void visitFunctionDefinition(FunctionDefinition node) {
-    if (node.thisParameter != null) {
-      setValue(node.thisParameter, nonConst());
-    }
     node.parameters.forEach(visit);
     setReachable(node.body);
   }
@@ -728,6 +725,11 @@ class _TypePropagationVisitor<T> implements Visitor {
     setValue(node, constantValue(value, typeSystem.typeOf(value)));
   }
 
+  void visitThis(This node) {
+    // TODO(karlklose): Add the type.
+    setValue(node, nonConst());
+  }
+
   void visitReifyTypeVar(ReifyTypeVar node) {
     setValue(node, nonConst(typeSystem.typeType));
   }