Make [HTypeConversion] with NO_CHECK code motion invariant to ensure no code is generated for it.

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 2273 matching lines @@
   bool get isBooleanConversionCheck => kind == BOOLEAN_CONVERSION_CHECK;
 
   accept(HVisitor visitor) => visitor.visitTypeConversion(this);
 
   bool isJsStatement() => isControlFlow();
   bool isControlFlow() => isArgumentTypeCheck || isReceiverTypeCheck;
   bool canThrow() => isChecked;
 
   int typeCode() => HInstruction.TYPE_CONVERSION_TYPECODE;
   bool typeEquals(HInstruction other) => other is HTypeConversion;
+  bool isCodeMotionInvariant() => kind == NO_CHECK;
 
   bool dataEquals(HTypeConversion other) {
     return kind == other.kind
         && typeExpression == other.typeExpression
         && instructionType == other.instructionType;
   }
 }
 
 class HRangeConversion extends HCheck {
   HRangeConversion(HInstruction input) : super(<HInstruction>[input]) {
@@ skipping 371 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);
 }