Introduce a PrototypeIterator template and use it all over the place

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index f076bdb481ff2348dcf49c586c9ef6c1dec13e1c..651205bf11199a150230715355acecc2fc8ea1b4 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -37,6 +37,7 @@
 #include "src/profile-generator-inl.h"
 #include "src/property.h"
 #include "src/property-details.h"
+#include "src/prototype-iterator.h"
 #include "src/runtime.h"
 #include "src/runtime-profiler.h"
 #include "src/scanner-character-streams.h"
@@ -3164,7 +3165,7 @@ Local<Value> v8::Object::GetPrototype() {
   ON_BAILOUT(isolate, "v8::Object::GetPrototype()", return Local<v8::Value>());
   ENTER_V8(isolate);
   i::Handle<i::Object> self = Utils::OpenHandle(this);
-  i::Handle<i::Object> result(self->GetPrototype(isolate), isolate);
+  i::Handle<i::Object> result(SAFE_GET_PROTOTYPE(isolate, *self), isolate);
   return Utils::ToLocal(result);
 }
 
@@ -3196,12 +3197,15 @@ Local<Object> v8::Object::FindInstanceInPrototypeChain(
   ENTER_V8(isolate);
   i::JSObject* object = *Utils::OpenHandle(this);
   i::FunctionTemplateInfo* tmpl_info = *Utils::OpenHandle(*tmpl);
-  while (!tmpl_info->IsTemplateFor(object)) {
-    i::Object* prototype = object->GetPrototype();
-    if (!prototype->IsJSObject()) return Local<Object>();
-    object = i::JSObject::cast(prototype);
+  for (i::PrototypeIterator<i::STORE_AS_POINTER, i::MAP_BASED_WALK,
+                            i::END_AT_NULL_VALUE> iter(object);
+       !iter.IsAtEnd(); iter.Advance()) {
+    if (tmpl_info->IsTemplateFor(iter.GetCurrent())) {
+      return Utils::ToLocal(
+          i::Handle<i::JSObject>(i::JSObject::cast(iter.GetCurrent())));
+    }
   }
-  return Utils::ToLocal(i::Handle<i::JSObject>(object));
+  return Local<Object>();
 }