Introduce a PrototypeIterator template and use it all over the place

src/accessors.cc

Index: src/accessors.cc
diff --git a/src/accessors.cc b/src/accessors.cc
index aeea430704d9f9956d7d9044fe51788a33be9996..cc755d98e9df74667c58cffab9da97a59ebb3795 100644
--- a/src/accessors.cc
+++ b/src/accessors.cc
@@ -15,6 +15,7 @@
 #include "src/isolate.h"
 #include "src/list-inl.h"
 #include "src/property-details.h"
+#include "src/prototype-iterator.h"
 
 namespace v8 {
 namespace internal {
@@ -67,8 +68,9 @@ Handle<ExecutableAccessorInfo> Accessors::CloneAccessor(
 
 template <class C>
 static C* FindInstanceOf(Isolate* isolate, Object* obj) {
-  for (Object* cur = obj; !cur->IsNull(); cur = cur->GetPrototype(isolate)) {
-    if (Is<C>(cur)) return C::cast(cur);
+  for (PrototypeIterator<STORE_AS_POINTER, TYPE_BASED_WALK, END_AT_NULL_VALUE>
+           iter(isolate, obj); !iter.IsAtEnd(); iter.Advance()) {
+    if (Is<C>(iter.GetCurrent())) return C::cast(iter.GetCurrent());
   }
   return NULL;
 }
@@ -774,8 +776,8 @@ static Handle<Object> GetFunctionPrototype(Isolate* isolate,
     JSFunction* function_raw = FindInstanceOf<JSFunction>(isolate, *receiver);
     if (function_raw == NULL) return isolate->factory()->undefined_value();
     while (!function_raw->should_have_prototype()) {
-      function_raw = FindInstanceOf<JSFunction>(isolate,
-                                                function_raw->GetPrototype());
+      function_raw = FindInstanceOf<JSFunction>(
+          isolate, SAFE_GET_PROTOTYPE_FAST(function_raw));
       // There has to be one because we hit the getter.
       ASSERT(function_raw != NULL);
     }