Don't gvn HForeignCode without source text

pkg/compiler/lib/src/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.
 
 import '../closure.dart';
 import '../common.dart';
 import '../compiler.dart' show Compiler;
 import '../constants/constant_system.dart';
 import '../constants/values.dart';
 import '../dart_types.dart';
@@ skipping 1922 matching lines @@
   }
 
   bool onlyThrowsNSM() => throwBehavior.isOnlyNullNSMGuard;
 
   bool get isAllocation =>
       nativeBehavior != null && nativeBehavior.isAllocation && !canBeNull();
 
   int typeCode() => HInstruction.FOREIGN_CODE_TYPECODE;
   bool typeEquals(other) => other is HForeignCode;
   bool dataEquals(HForeignCode other) {
-    return codeTemplate.source == other.codeTemplate.source;
+    return codeTemplate.source != null &&
+        codeTemplate.source == other.codeTemplate.source;
   }
 
-  String toString() => 'HForeignCode("${codeTemplate.source}", $inputs)';
+  String toString() => 'HForeignCode("${codeTemplate.source}")';
 }
 
 abstract class HInvokeBinary extends HInstruction {
   final Selector selector;
   HInvokeBinary(
       HInstruction left, HInstruction right, this.selector, TypeMask type)
       : super(<HInstruction>[left, right], type) {
     sideEffects.clearAllSideEffects();
     sideEffects.clearAllDependencies();
     setUseGvn();
@@ skipping 1513 matching lines @@
 class HDynamicType extends HRuntimeType {
   HDynamicType(DynamicType dartType, TypeMask instructionType)
       : super(const <HInstruction>[], dartType, instructionType);
 
   accept(HVisitor visitor) => visitor.visitDynamicType(this);
 
   int typeCode() => HInstruction.DYNAMIC_TYPE_TYPECODE;
 
   bool typeEquals(HInstruction other) => other is HDynamicType;
 }