cps_ir: interceptor calling convention, operator== prologue

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

Index: pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
diff --git a/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart b/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
index d16fd8c84ed136bb8520ef030f4740f142b60ddb..0275822f936393393b5ced1237fd104d0a3a61f9 100644
--- a/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
+++ b/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
@@ -327,6 +327,8 @@ class InvokeMethod extends Expression implements Invoke {
 /// [receiver] may refer to a null constant primitive. This happens for direct
 /// invocations to intercepted methods, where the effective receiver is instead
 /// passed as a formal parameter.
+/// TODO(sra): Review. A direct call to a method that is mixed into a native
+/// class will still require an explicit argument.
 ///
 /// When targeting Dart, this instruction is used to represent super calls.
 /// Here, [receiver] must always be a reference to `this`, and [target] must be