VectorICs: recent changes broke cases with --novector-ics

Ensure that we protect turning off the vector ics flag.

BUG=
R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/1087213002

Cr-Commit-Position: refs/heads/master@{#27844}

src/hydrogen.cc

@@ -6927,7 +6927,7 @@ HInstruction* HOptimizedGraphBuilder::BuildKeyedGeneric(
         New<HLoadKeyedGeneric>(object, key, initial_state);
     // HLoadKeyedGeneric with vector ics benefits from being encoded as
     // MEGAMORPHIC because the vector/slot combo becomes unnecessary.
-    if (initial_state != MEGAMORPHIC) {
+    if (FLAG_vector_ics && initial_state != MEGAMORPHIC) {
       // We need to pass vector information.
       Handle<TypeFeedbackVector> vector =
           handle(current_feedback_vector(), isolate());

src/type-feedback-vector.cc

@@ -139,6 +139,8 @@ Handle<TypeFeedbackVector> TypeFeedbackVector::Copy(
 
 bool TypeFeedbackVector::SpecDiffersFrom(
     const ZoneFeedbackVectorSpec* other_spec) const {
+  if (!FLAG_vector_ics) return false;
+
   if (other_spec->slots() != Slots() || other_spec->ic_slots() != ICSlots()) {
     return true;
   }