dart2js cleanup: remove unused imports and variables

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

Index: pkg/compiler/lib/src/js_emitter/program_builder/program_builder.dart
diff --git a/pkg/compiler/lib/src/js_emitter/program_builder/program_builder.dart b/pkg/compiler/lib/src/js_emitter/program_builder/program_builder.dart
index 5d5afe69ade4becffae1e4663635be1076f7d1b7..145070f9cba1709f7e69897daaf8e965c86ad9ae 100644
--- a/pkg/compiler/lib/src/js_emitter/program_builder/program_builder.dart
+++ b/pkg/compiler/lib/src/js_emitter/program_builder/program_builder.dart
@@ -4,19 +4,6 @@
 
 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;
@@ -25,6 +12,7 @@ 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,
@@ -36,7 +24,6 @@ import '../../elements/elements.dart'
         GetterElement,
         LibraryElement,
         MethodElement,
-        Name,
         ParameterElement,
         TypedefElement,
         VariableElement;
@@ -46,11 +33,22 @@ 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 'registry.dart';
 part 'field_visitor.dart';
+part 'registry.dart';
 
 /// Builds a self-contained representation of the program that can then be
 /// emitted more easily by the individual emitters.