Introduce FeedbackVectorSlot type - better than int.

src/type-info.h

Index: src/type-info.h
diff --git a/src/type-info.h b/src/type-info.h
index 1343e0a76bf865015b93a3343946cb22e4d4a51a..5c99e71d550a1e190a169039e3a05b5c36de8d3f 100644
--- a/src/type-info.h
+++ b/src/type-info.h
@@ -25,16 +25,16 @@ class TypeFeedbackOracle: public ZoneObject {
 
   bool LoadIsUninitialized(TypeFeedbackId id);
   bool StoreIsUninitialized(TypeFeedbackId id);
-  bool CallIsMonomorphic(int slot);
+  bool CallIsMonomorphic(FeedbackVectorSlot slot);
   bool CallIsMonomorphic(TypeFeedbackId aid);
   bool KeyedArrayCallIsHoley(TypeFeedbackId id);
-  bool CallNewIsMonomorphic(int slot);
+  bool CallNewIsMonomorphic(FeedbackVectorSlot slot);
 
   // TODO(1571) We can't use ForInStatement::ForInType as the return value due
   // to various cycles in our headers.
   // TODO(rossberg): once all oracle access is removed from ast.cc, it should
   // be possible.
-  byte ForInType(int feedback_vector_slot);
+  byte ForInType(FeedbackVectorSlot feedback_vector_slot);
 
   KeyedAccessStoreMode GetStoreMode(TypeFeedbackId id);
 
@@ -59,10 +59,10 @@ class TypeFeedbackOracle: public ZoneObject {
   static bool CanRetainOtherContext(JSFunction* function,
                                     Context* native_context);
 
-  Handle<JSFunction> GetCallTarget(int slot);
-  Handle<AllocationSite> GetCallAllocationSite(int slot);
-  Handle<JSFunction> GetCallNewTarget(int slot);
-  Handle<AllocationSite> GetCallNewAllocationSite(int slot);
+  Handle<JSFunction> GetCallTarget(FeedbackVectorSlot slot);
+  Handle<AllocationSite> GetCallAllocationSite(FeedbackVectorSlot slot);
+  Handle<JSFunction> GetCallNewTarget(FeedbackVectorSlot slot);
+  Handle<AllocationSite> GetCallNewAllocationSite(FeedbackVectorSlot slot);
 
   bool LoadIsBuiltin(TypeFeedbackId id, Builtins::Name builtin_id);
 
@@ -112,7 +112,7 @@ class TypeFeedbackOracle: public ZoneObject {
 
   // Returns an element from the type feedback vector. Returns undefined
   // if there is no information.
-  Handle<Object> GetInfo(int slot);
+  Handle<Object> GetInfo(FeedbackVectorSlot slot);
 
  private:
   Handle<Context> native_context_;