Address review comments on issue 11412105.

sdk/lib/_internal/compiler/implementation/ssa/codegen.dart

Index: sdk/lib/_internal/compiler/implementation/ssa/codegen.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/ssa/codegen.dart	(revision 15278)
+++ sdk/lib/_internal/compiler/implementation/ssa/codegen.dart	(working copy)
@@ -1724,6 +1724,9 @@
     use(node.receiver);
     if (node.element == backend.jsArrayLength
         || node.element == backend.jsStringLength) {
+      // 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 = backend.namer.getName(node.element);
@@ -1737,21 +1740,6 @@
     }
   }
 
-  // Determine if an instruction is a simple number computation
-  // involving only things with guaranteed number types and a given
-  // field.
-  bool isSimpleFieldNumberComputation(HInstruction value, HFieldSet node) {
-    if (value.guaranteedType.union(HType.NUMBER, compiler) == HType.NUMBER) {
-      return true;
-    }
-    if (value is HBinaryArithmetic) {
-      return (isSimpleFieldNumberComputation(value.left, node) &&
-              isSimpleFieldNumberComputation(value.right, node));
-    }
-    if (value is HFieldGet) return value.element == node.element;
-    return false;
-  }
-
   visitFieldSet(HFieldSet node) {
     String name = backend.namer.getName(node.element);
     DartType type = types[node.receiver].computeType(compiler);