Optimize Crankshaft array literal initialization from boilerplate.

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index 32c3abfe7baa0b5f567478c08a3533e538151113..31d7d153f9b36a51ccef8ad76609bcb0a54debfd 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -1227,10 +1227,7 @@ void HConstant::PrintDataTo(StringStream* stream) {
 
 
 bool HArrayLiteral::IsCopyOnWrite() const {
-  Handle<FixedArray> constant_elements = this->constant_elements();
-  FixedArrayBase* constant_elements_values =
-      FixedArrayBase::cast(constant_elements->get(1));
-  return constant_elements_values->map() == HEAP->fixed_cow_array_map();
+  return boilerplate_object_->elements()->map() == HEAP->fixed_cow_array_map();
 }