[ic] Avoid feedback metadata names table reallocations.

An attempt to fix memory regression (r38047) caused another regression
because custom capacity chosen for names dictionary implied reallocations
during initialization in some cases.

BUG=chromium:625894,chromium:632231

Review-Url: https://codereview.chromium.org/2394873002
Cr-Commit-Position: refs/heads/master@{#40006}

src/type-feedback-vector.cc

@@ -102,9 +102,7 @@ Handle<TypeFeedbackMetadata> TypeFeedbackMetadata::New(Isolate* isolate,
 
   Handle<UnseededNumberDictionary> names;
   if (name_count) {
-    names = UnseededNumberDictionary::New(
-        isolate, base::bits::RoundUpToPowerOfTwo32(name_count), TENURED,
-        USE_CUSTOM_MINIMUM_CAPACITY);
+    names = UnseededNumberDictionary::New(isolate, name_count, TENURED);
   }
 
   int name_index = 0;
@@ -114,7 +112,10 @@ Handle<TypeFeedbackMetadata> TypeFeedbackMetadata::New(Isolate* isolate,
     if (SlotRequiresName(kind)) {
       Handle<String> name = spec->GetName(name_index);
       DCHECK(!name.is_null());
-      names = UnseededNumberDictionary::AtNumberPut(names, i, name);
+      Handle<UnseededNumberDictionary> new_names =
+          UnseededNumberDictionary::AtNumberPut(names, i, name);
+      DCHECK_EQ(*new_names, *names);
+      names = new_names;
       name_index++;
     }
   }