Use platform specific stubs for vector-based Load/KeyedLoad.

test/cctest/test-feedback-vector.cc

Index: test/cctest/test-feedback-vector.cc
diff --git a/test/cctest/test-feedback-vector.cc b/test/cctest/test-feedback-vector.cc
index fe7198cded852d63a4bb3e3001dc4abe3483a023..d375ba36a0b79c69755aca8dac7718f08f715a3d 100644
--- a/test/cctest/test-feedback-vector.cc
+++ b/test/cctest/test-feedback-vector.cc
@@ -71,8 +71,8 @@ TEST(VectorStructure) {
   CHECK_EQ(index,
            TypeFeedbackVector::kReservedIndexCount + metadata_length + 3);
   CHECK(FeedbackVectorICSlot(0) == vector->ToICSlot(index));
-
-  CHECK_EQ(TypeFeedbackVector::kReservedIndexCount + metadata_length + 3 + 5,
+  CHECK_EQ(TypeFeedbackVector::kReservedIndexCount + metadata_length + 3 +
+               5 * TypeFeedbackVector::elements_per_ic_slot(),
            vector->length());
 }