Introduce {ConstantElementsPair} struct for type safety.

src/crankshaft/hydrogen.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/crankshaft/hydrogen.h"
 
 #include <memory>
 #include <sstream>
 
 #include "src/allocation-site-scopes.h"
@@ skipping 5624 matching lines @@
   if (!boilerplate_object.is_null() &&
       IsFastLiteral(boilerplate_object, kMaxFastLiteralDepth,
                     &max_properties)) {
     DCHECK(site->SitePointsToLiteral());
     AllocationSiteUsageContext site_context(isolate(), site, false);
     site_context.EnterNewScope();
     literal = BuildFastLiteral(boilerplate_object, &site_context);
     site_context.ExitScope(site, boilerplate_object);
   } else {
     NoObservableSideEffectsScope no_effects(this);
-    Handle<FixedArray> constants = expr->constant_elements();
+    Handle<ConstantElementsPair> constants = expr->constant_elements();
     int literal_index = expr->literal_index();
     int flags = expr->ComputeFlags(true);
 
     Add<HPushArguments>(AddThisFunction(), Add<HConstant>(literal_index),
                         Add<HConstant>(constants), Add<HConstant>(flags));
 
     Runtime::FunctionId function_id = Runtime::kCreateArrayLiteral;
     literal = Add<HCallRuntime>(Runtime::FunctionForId(function_id), 4);
 
     // Register to deopt if the boilerplate ElementsKind changes.
@@ skipping 7382 matching lines @@
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 }  // namespace internal
 }  // namespace v8