Hook up the --minify option in dart2js and use it to get rid of unnecessary whitespace inside funct…

lib/compiler/implementation/js_backend/backend.dart

 // Copyright (c) 2012, 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.
 
 typedef void Recompile(Element element);
 
 class ReturnInfo {
   HType returnType;
   List<Element> compiledFunctions;
 
@@ skipping 244 matching lines @@
   final HTypeMap types;
 
   JavaScriptItemCompilationContext() : types = new HTypeMap();
 }
 
 class JavaScriptBackend extends Backend {
   SsaBuilderTask builder;
   SsaOptimizerTask optimizer;
   SsaCodeGeneratorTask generator;
   CodeEmitterTask emitter;
+
   final Map<Element, Map<Element, HType>> fieldInitializers;
   final Map<Element, Map<Element, HType>> fieldConstructorSetters;
   final Map<Element, Map<Element, HType>> fieldSettersType;
 
   final Map<Element, ReturnInfo> returnInfo;
 
   final List<Element> invalidateAfterCodegen;
   ArgumentTypesRegistry argumentTypes;
 
   List<CompilerTask> get tasks {
@@ skipping 224 matching lines @@
   HType optimisticReturnTypesWithRecompilationOnTypeChange(
       FunctionElement caller, FunctionElement callee) {
     returnInfo.putIfAbsent(callee, () => new ReturnInfo.unknownType());
     ReturnInfo info = returnInfo[callee];
     if (info.returnType != HType.UNKNOWN && caller != null) {
       info.addCompiledFunction(caller);
     }
     return info.returnType;
   }
 }