VectorICs: megamorphic keyed loads in crankshaft don't need a vector.

src/code-factory.cc

Index: src/code-factory.cc
diff --git a/src/code-factory.cc b/src/code-factory.cc
index 71c5449aaaadbba0477fe2fe9de5034bb694132b..60361da80322831faf24d97967377f1abc1f8617 100644
--- a/src/code-factory.cc
+++ b/src/code-factory.cc
@@ -53,7 +53,7 @@ Callable CodeFactory::KeyedLoadICInOptimizedCode(
     Isolate* isolate, InlineCacheState initialization_state) {
   auto code = KeyedLoadIC::initialize_stub_in_optimized_code(
       isolate, initialization_state);
-  if (FLAG_vector_ics) {
+  if (FLAG_vector_ics && initialization_state != MEGAMORPHIC) {
     return Callable(code, VectorLoadICDescriptor(isolate));
   }
   return Callable(code, LoadDescriptor(isolate));