Fix performance regression after adding inlining support for operators, [], and []=.

sdk/lib/_internal/compiler/implementation/ssa/nodes.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;
 
 abstract class HVisitor<R> {
   R visitAdd(HAdd node);
   R visitBailoutTarget(HBailoutTarget node);
   R visitBitAnd(HBitAnd node);
@@ skipping 1109 matching lines @@
  * being done reference the [HCheck] instruction instead of the
  * instruction itself.
  */
 abstract class HCheck extends HInstruction {
   HCheck(inputs) : super(inputs) {
     setUseGvn();
   }
   HInstruction get checkedInput => inputs[0];
   bool isJsStatement() => true;
   bool canThrow() => true;
+
+  HInstruction unwrap() {
+    var checked = checkedInput;
+    while (checked is HCheck) checked = checked.checkedInput;
+    return checked;
+  }
 }
 
 class HBailoutTarget extends HInstruction {
   final int state;
   bool isEnabled = true;
   // For each argument we record how many dummy (unused) arguments should
   // precede it, to make sure it lands in the correctly named parameter in the
   // bailout function.
   List<int> padding;
   HBailoutTarget(this.state) : super(<HInstruction>[]) {
@@ skipping 1458 matching lines @@
   HBasicBlock get start => expression.start;
   HBasicBlock get end {
     // We don't create a switch block if there are no cases.
     assert(!statements.isEmpty);
     return statements.last.end;
   }
 
   bool accept(HStatementInformationVisitor visitor) =>
       visitor.visitSwitchInfo(this);
 }