Optimize length access on all JSIndexable things.

sdk/lib/_internal/compiler/implementation/ssa/codegen.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.
 
 part of ssa;
 
 class SsaCodeGeneratorTask extends CompilerTask {
 
   final JavaScriptBackend backend;
 
@@ skipping 1630 matching lines @@
       js.PropertyAccess method =
           new js.PropertyAccess.field(prototype, methodName);
       push(jsPropertyCall(method, "call", visitArguments(node.inputs)), node);
     }
     world.registerStaticUse(superMethod);
   }
 
   visitFieldGet(HFieldGet node) {
     use(node.receiver);
     Element element = node.element;
-    if (element == backend.jsArrayLength || element == backend.jsStringLength) {
+    if (element == backend.jsIndexableLength) {
       // We're accessing a native JavaScript property called 'length'
       // on a JS String or a JS array. Therefore, the name of that
       // property should not be mangled.
       push(new js.PropertyAccess.field(pop(), 'length'), node);
     } else {
       String name = _fieldPropertyName(element);
       push(new js.PropertyAccess.field(pop(), name), node);
       world.registerFieldGetter(element);
     }
   }
@@ skipping 1328 matching lines @@
   if (leftType.canBeNull() && rightType.canBeNull()) {
     if (left.isConstantNull() || right.isConstantNull() ||
         (leftType.isPrimitive() && leftType == rightType)) {
       return '==';
     }
     return null;
   } else {
     return '===';
   }
 }