Tighten up handling of JS types and add test.

pkg/dev_compiler/lib/src/compiler/code_generator.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:collection' show HashMap, HashSet;
 import 'dart:math' show min, max;
 
 import 'package:analyzer/analyzer.dart' hide ConstantEvaluator;
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 419 matching lines @@
     if (e == null ||
         e.library == null ||
         findAnnotation(e.library, isPublicJSAnnotation) == null) {
       return null;
     }
     if (e is PropertyInducingElement) {
       // Assume properties have consistent JS names for getters and setters.
       return _jsInteropStaticMemberName(e.getter, name: e.name) ??
           _jsInteropStaticMemberName(e.setter, name: e.name);
     }
-    if (e is ExecutableElement &&
-        e.isExternal &&
-        findAnnotation(e, isPublicJSAnnotation) != null) {
+    if (e is ExecutableElement && e.isExternal) {
       return getAnnotationName(e, isPublicJSAnnotation) ?? name ?? e.name;
     }
     return null;
   }
 
   JS.Expression _emitJSInteropStaticMemberName(Element e) {
     var name = _jsInteropStaticMemberName(e);
     if (name == null) return null;
     // We do not support statics names with JS annotations containing dots.
     // See https://github.com/dart-lang/sdk/issues/27926
@@ skipping 5665 matching lines @@
   if (targetIdentifier.staticElement is! PrefixElement) return false;
   var prefix = targetIdentifier.staticElement as PrefixElement;
 
   // The library the prefix is referring to must come from a deferred import.
   var containingLibrary = resolutionMap
       .elementDeclaredByCompilationUnit(target.root as CompilationUnit)
       .library;
   var imports = containingLibrary.getImportsWithPrefix(prefix);
   return imports.length == 1 && imports[0].isDeferred;
 }