Reapply class/method/field minification

sdk/lib/_internal/compiler/implementation/js_backend/backend.dart

Index: sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart b/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
index a566b0f42434941147d8aa240c8bc6625e968a11..902414dbf26f44ef90e0fa8b66118dac84af81b7 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
@@ -700,10 +700,8 @@ class JavaScriptBackend extends Backend {
 
   final RuntimeTypeInformation rti;
 
-  JavaScriptBackend(Compiler compiler,
-                    bool generateSourceMap,
-                    bool disableEval)
-      : namer = new Namer(compiler),
+  JavaScriptBackend(Compiler compiler, bool generateSourceMap, bool disableEval)
+      : namer = determineNamer(compiler),
         returnInfo = new Map<Element, ReturnInfo>(),
         invalidateAfterCodegen = new List<Element>(),
         interceptors = new Interceptors(compiler),
@@ -724,6 +722,12 @@ class JavaScriptBackend extends Backend {
     fieldTypes = new FieldTypesRegistry(this);
   }
 
+  static Namer determineNamer(Compiler compiler) {
+    return compiler.enableMinification ?
+        new MinifyNamer(compiler) :
+        new Namer(compiler);
+  }
+
   bool isInterceptorClass(Element element) {
     if (element == null) return false;
     return interceptedClasses.containsKey(element);