Handlify Object::GetPrototype and (most) callers.

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index b93df482861615d499b3b4668143e2537ca9bab4..404c4e7ec86b5a063a9cbc83a3b73a8fcb2f7748 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -6355,14 +6355,14 @@ HInstruction* HOptimizedGraphBuilder::BuildMonomorphicElementAccess(
     // changes could allow callbacks on elements in the chain that
     // aren't compatible with monomorphic keyed stores.
     Handle<JSObject> prototype(JSObject::cast(map->prototype()));
-    Object* holder = map->prototype();
-    while (holder->GetPrototype(isolate())->IsJSObject()) {
-      holder = holder->GetPrototype(isolate());
+    Handle<Object> holder(map->prototype(), isolate());
+    while (Object::GetPrototype(isolate(), holder)->IsJSObject()) {
+      holder = Object::GetPrototype(isolate(), holder);
     }
-    ASSERT(holder->GetPrototype(isolate())->IsNull());
+    ASSERT(Object::GetPrototype(isolate(), holder)->IsNull());
 
     BuildCheckPrototypeMaps(prototype,
-                            Handle<JSObject>(JSObject::cast(holder)));
+                            Handle<JSObject>(JSObject::cast(*holder)));
   }
 
   LoadKeyedHoleMode load_mode = BuildKeyedHoleMode(map);