Introduce LiteralsArray to hide it's implementation.

src/full-codegen/arm64/full-codegen-arm64.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.
 
 #if V8_TARGET_ARCH_ARM64
 
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
 #include "src/compiler.h"
@@ skipping 1469 matching lines @@
   Label materialized;
   // Registers will be used as follows:
   // x5 = materialized value (RegExp literal)
   // x4 = JS function, literals array
   // x3 = literal index
   // x2 = RegExp pattern
   // x1 = RegExp flags
   // x0 = RegExp literal clone
   __ Ldr(x10, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
   __ Ldr(x4, FieldMemOperand(x10, JSFunction::kLiteralsOffset));
-  int literal_offset =
-      FixedArray::kHeaderSize + expr->literal_index() * kPointerSize;
+  int literal_offset = LiteralsArray::OffsetOfLiteralAt(expr->literal_index());
   __ Ldr(x5, FieldMemOperand(x4, literal_offset));
   __ JumpIfNotRoot(x5, Heap::kUndefinedValueRootIndex, &materialized);
 
   // Create regexp literal using runtime function.
   // Result will be in x0.
   __ Mov(x3, Smi::FromInt(expr->literal_index()));
   __ Mov(x2, Operand(expr->pattern()));
   __ Mov(x1, Operand(expr->flags()));
   __ Push(x4, x3, x2, x1);
   __ CallRuntime(Runtime::kMaterializeRegExpLiteral, 4);
@@ skipping 3756 matching lines @@
   }
 
   return INTERRUPT;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM64