dart2js cleanup: remove unused imports and variables

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

 // Copyright (c) 2014, 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.
 
 library dart2js.js_emitter.program_builder;
 
-import '../js_emitter.dart'
-    show
-        ClassStubGenerator,
-        CodeEmitterTask,
-        computeMixinClass,
-        Emitter,
-        InterceptorStubGenerator,
-        MainCallStubGenerator,
-        ParameterStubGenerator,
-        RuntimeTypeGenerator,
-        TypeTestProperties;
-import '../model.dart';
-
 import '../../closure.dart' show ClosureFieldElement;
 import '../../common.dart';
 import '../../common/names.dart' show Names, Selectors;
 import '../../compiler.dart' show Compiler;
 import '../../constants/values.dart'
     show ConstantValue, InterceptorConstantValue;
 import '../../core_types.dart' show CoreClasses;
 import '../../dart_types.dart' show DartType, FunctionType, TypedefType;
+import '../../deferred_load.dart' show DeferredLoadTask, OutputUnit;
 import '../../elements/elements.dart'
     show
         ClassElement,
         Element,
         Elements,
         FieldElement,
         FunctionElement,
         FunctionSignature,
         GetterElement,
         LibraryElement,
         MethodElement,
-        Name,
         ParameterElement,
         TypedefElement,
         VariableElement;
 import '../../js/js.dart' as js;
 import '../../js_backend/backend_helpers.dart' show BackendHelpers;
 import '../../js_backend/js_backend.dart'
     show Namer, JavaScriptBackend, JavaScriptConstantCompiler, StringBackedName;
 import '../../universe/selector.dart' show Selector;
 import '../../universe/universe.dart' show Universe, SelectorConstraints;
-import '../../deferred_load.dart' show DeferredLoadTask, OutputUnit;
+import '../js_emitter.dart'
+    show
+        ClassStubGenerator,
+        CodeEmitterTask,
+        computeMixinClass,
+        Emitter,
+        InterceptorStubGenerator,
+        MainCallStubGenerator,
+        ParameterStubGenerator,
+        RuntimeTypeGenerator,
+        TypeTestProperties;
+import '../model.dart';
 
 part 'collector.dart';
+part 'field_visitor.dart';
 part 'registry.dart';
-part 'field_visitor.dart';
 
 /// Builds a self-contained representation of the program that can then be
 /// emitted more easily by the individual emitters.
 class ProgramBuilder {
   final Compiler _compiler;
   final Namer namer;
   final CodeEmitterTask _task;
 
   /// Contains the collected information the program builder used to build
   /// the model.
@@ skipping 913 matching lines @@
       Constant constant = new Constant(name, holder, constantValue);
       _constants[constantValue] = constant;
     }
   }
 
   Holder _registerStaticStateHolder() {
     return _registry.registerHolder(namer.staticStateHolder,
         isStaticStateHolder: true);
   }
 }