dart2js cleanup: remove unused imports and variables

pkg/compiler/lib/src/js_backend/js_interop_analysis.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.
 
 /// Analysis to determine how to generate code for typed JavaScript interop.
 library compiler.src.js_backend.js_interop_analysis;
 
+import '../constants/values.dart'
+    show ConstantValue, ConstructedConstantValue, StringConstantValue;
 import '../diagnostics/messages.dart' show MessageKind;
-import '../constants/values.dart'
-    show
-        ConstantValue,
-        ConstructedConstantValue,
-        ListConstantValue,
-        NullConstantValue,
-        StringConstantValue,
-        TypeConstantValue;
 import '../elements/elements.dart'
     show
         ClassElement,
         Element,
         FieldElement,
         FunctionElement,
         LibraryElement,
         ParameterElement,
         MetadataAnnotation;
-
 import '../js/js.dart' as jsAst;
 import '../js/js.dart' show js;
 import '../universe/selector.dart' show Selector;
 import '../universe/universe.dart' show SelectorConstraints;
-
 import 'backend_helpers.dart' show BackendHelpers;
 import 'js_backend.dart' show JavaScriptBackend;
 
 class JsInteropAnalysis {
   final JavaScriptBackend backend;
 
   /// The resolved [FieldElement] for `Js.name`.
   FieldElement nameField;
   bool enabledJsInterop = false;
 
@@ skipping 142 matching lines @@
           var name = backend.namer.invocationName(selector);
           statements.add(js.statement(
               'Function.prototype.# = function(#) { return this(#) }',
               [name, parameters, parameters]));
         }
       });
     });
     return new jsAst.Block(statements);
   }
 }