Revert "Make ClosureTask only accept Element-level APIs instead of resolvedAst."

pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart

Index: pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart
diff --git a/pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart b/pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart
index ac562b6988635cf0d5fb78c6bf2aa10ff1379540..3d12635d1bdc878719eaf802db8942c5af6c14e9 100644
--- a/pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart
+++ b/pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart
@@ -121,7 +121,7 @@ class RuntimeTypeGenerator {
       jsAst.Expression thisAccess = new jsAst.This();
       if (!method.isAbstract) {
         ClosureClassMap closureData =
-            _closureToClassMapper.getClosureToClassMapping(method);
+            _closureToClassMapper.getClosureToClassMapping(method.resolvedAst);
         if (closureData != null) {
           ClosureFieldElement thisLocal =
               closureData.freeVariableMap[closureData.thisLocal];