Introduce TypeFeedbackVector, as FixedArray grew constrictive.

src/factory.h

Index: src/factory.h
diff --git a/src/factory.h b/src/factory.h
index 47b16f59fb480ebe151b67c5822a7cee86d28b25..24b490c3443961828d9f4529d34013acd937be36 100644
--- a/src/factory.h
+++ b/src/factory.h
@@ -600,12 +600,12 @@ class Factory FINAL {
   Handle<SharedFunctionInfo> NewSharedFunctionInfo(
       Handle<String> name, int number_of_literals, FunctionKind kind,
       Handle<Code> code, Handle<ScopeInfo> scope_info,
-      Handle<FixedArray> feedback_vector);
+      Handle<TypeFeedbackVector> feedback_vector);
   Handle<SharedFunctionInfo> NewSharedFunctionInfo(Handle<String> name,
                                                    MaybeHandle<Code> code);
 
   // Allocate a new type feedback vector
-  Handle<FixedArray> NewTypeFeedbackVector(int slot_count);
+  Handle<TypeFeedbackVector> NewTypeFeedbackVector(int slot_count);
 
   // Allocates a new JSMessageObject object.
   Handle<JSMessageObject> NewJSMessageObject(