Make the ClosedWorld build the closure class on the kernel side.

pkg/compiler/lib/src/common/codegen.dart

Index: pkg/compiler/lib/src/common/codegen.dart
diff --git a/pkg/compiler/lib/src/common/codegen.dart b/pkg/compiler/lib/src/common/codegen.dart
index 00b49253ea2e503d2e39491961a18c8b021b4702..4fcf7b8ef8bdc7f81164ed4bc4b09da004b97748 100644
--- a/pkg/compiler/lib/src/common/codegen.dart
+++ b/pkg/compiler/lib/src/common/codegen.dart
@@ -147,7 +147,7 @@ class CodegenRegistry {
     worldImpact.registerTypeVariableBoundsSubtypeCheck(subtype, supertype);
   }
 
-  void registerInstantiatedClosure(LocalFunctionElement element) {
+  void registerInstantiatedClosure(Local element) {

[sra1, 2017/07/28 20:38:51]

assert this is a function that can be used to find the synthetic closure class

[Emily Fortuna, 2017/07/28 21:37:06]

You're right, this isn't an easy fix. I put it back to LocalFunctionElement and
updated the status file.

Johnni, can you please take a look at this? Basically we have a JLocal, but a
little further on we expect it to be a KLocalFunction (and it would be nice to
be sure that the thing passed in is a form of LocalFunction rather than just a
Local). I'm not sure if this is due to not having propagated K->J throughout the
backend or if I should be storing a different local type for the "original"
closure.

[Johnni Winther, 2017/07/31 10:54:28]

It is okay to use [Local] here. Long term we should just register the
call-method instead (we use it to compute if the signature is needed for RTI).

     worldImpact.registerStaticUse(new StaticUse.closure(element));
   }