Introduce a PrototypeIterator class and use it for prototype access

src/ic.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/arguments.h"
 #include "src/codegen.h"
 #include "src/conversions.h"
 #include "src/execution.h"
 #include "src/ic-inl.h"
+#include "src/prototype.h"
 #include "src/runtime.h"
 #include "src/stub-cache.h"
 
 namespace v8 {
 namespace internal {
 
 char IC::TransitionMarkFromState(IC::State state) {
   switch (state) {
     case UNINITIALIZED: return '0';
     case PREMONOMORPHIC: return '.';
@@ skipping 217 matching lines @@
       Code::ExtractCacheHolderFromFlags(target()->flags());
 
   switch (cache_holder) {
     case OWN_MAP:
       // The stub was generated for JSObject but called for non-JSObject.
       // IC::GetCodeCacheHolder is not applicable.
       if (!receiver->IsJSObject()) return false;
       break;
     case PROTOTYPE_MAP:
       // IC::GetCodeCacheHolder is not applicable.
-      if (receiver->GetPrototype(isolate())->IsNull()) return false;
+      PrototypeIterator iter(isolate(), receiver);
+      if (iter.IsAtEnd()) return false;
       break;
   }
 
   Handle<Map> map(
       IC::GetCodeCacheHolder(isolate(), *receiver, cache_holder)->map());
 
   // Decide whether the inline cache failed because of changes to the
   // receiver itself or changes to one of its prototypes.
   //
   // If there are changes to the receiver itself, the map of the
@@ skipping 2835 matching lines @@
 #undef ADDR
 };
 
 
 Address IC::AddressFromUtilityId(IC::UtilityId id) {
   return IC_utilities[id];
 }
 
 
 } }  // namespace v8::internal