Re-apply issue 11308169: GVN getInterceptor and use the interceptor constant when the type is known.

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 2361 matching lines @@
 class HInterceptor extends HInstruction {
   final Set<ClassElement> interceptedClasses;
   HInterceptor(this.interceptedClasses, HInstruction receiver)
       : super(<HInstruction>[receiver]);
   String toString() => 'interceptor on $interceptedClasses';
   accept(HVisitor visitor) => visitor.visitInterceptor(this);
   HInstruction get receiver => inputs[0];
 
   void prepareGvn(HTypeMap types) {
     clearAllSideEffects();
+    setUseGvn();
   }
 
   int typeCode() => HInstruction.INTERCEPTOR_TYPECODE;
+  bool typeEquals(other) => other is HInterceptor;
 }
 
 /** An [HLazyStatic] is a static that is initialized lazily at first read. */
 class HLazyStatic extends HStatic {
   HLazyStatic(Element element) : super(element);
 
   void prepareGvn(HTypeMap types) {
     // TODO(4931): The first access has side-effects, but we afterwards we
     // should be able to GVN.
     setAllSideEffects();
@@ skipping 537 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);
 }