Fix some bugs that blocked optimizations in the new IRs.

pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart

 // Copyright (c) 2013, 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.ir_builder;
 
 import '../constants/expressions.dart';
 import '../constants/values.dart' show PrimitiveConstantValue;
 import '../dart_types.dart';
 import '../dart2jslib.dart';
@@ skipping 1628 matching lines @@
   ir.Primitive buildFunctionExpression(ir.FunctionDefinition definition) {
     ir.CreateFunction prim = new ir.CreateFunction(definition);
     add(new ir.LetPrim(prim));
     return prim;
   }
 
   /// Create a read access of [local].
   ir.Primitive buildLocalGet(LocalElement local) {
     assert(isOpen);
     if (isInClosureVariable(local)) {
-      ir.Primitive result = new ir.GetClosureVariable(getClosureVariable(local));
-      result.useElementAsHint(local);
+      // Do not use [local] as a hint on [result]. The variable should always
+      // be inlined, but the hint prevents it.
+      ir.Primitive result =
+          new ir.GetClosureVariable(getClosureVariable(local));
       add(new ir.LetPrim(result));
       return result;
     } else {
       return environment.lookup(local);
     }
   }
 
   /// Create a write access to [local] with the provided [value].
   ir.Primitive buildLocalSet(LocalElement local, ir.Primitive value) {
     assert(isOpen);
@@ skipping 215 matching lines @@
 
   ClosureEnvironment(this.selfReference, this.thisLocal, this.freeVariables);
 }
 
 /// Information about which variables are captured in a closure.
 /// This is used by the [DartIrBuilder] instead of [ClosureScope] and
 /// [ClosureEnvironment].
 abstract class ClosureVariableInfo {
   Iterable<Local> get capturedVariables;
 }