Move CodeGenerator::DescriptorList into shared part.

runtime/vm/code_generator_arm.h

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_CODE_GENERATOR_ARM_H_
 #define VM_CODE_GENERATOR_ARM_H_
 
 #ifndef VM_CODE_GENERATOR_H_
 #error Do not include code_generator_arm.h directly; use assembler.h instead.
 #endif
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
 
 namespace dart {
 
 // Forward declarations.
 class Assembler;
 class AstNode;
 class ParsedFunction;
 
 class CodeGenerator : public AstNodeVisitor {
  public:
-  CodeGenerator(Assembler* assembler, const ParsedFunction& parsed_function) { }
+  CodeGenerator(Assembler* assembler, const ParsedFunction& parsed_function)
+      : pc_descriptors_list_(NULL) { }
   virtual ~CodeGenerator() { }
 
   bool GenerateCode() {
     return false;
   }
 
   // Add exception handler table to code.
   void FinalizeExceptionHandlers(const Code& code) { UNIMPLEMENTED(); }
 
   // Add pc descriptors to code.
   void FinalizePcDescriptors(const Code& code) { UNIMPLEMENTED(); }
 
   // Add local variable descriptors to code.
   void FinalizeVarDescriptors(const Code& code) { UNIMPLEMENTED(); }
 
   // Allocate and return an arguments descriptor.
   // Let 'num_names' be the length of 'optional_arguments_names'.
   // Treat the first 'num_arguments - num_names' arguments as positional and
   // treat the following 'num_names' arguments as named optional arguments.
   static const Array& ArgumentsDescriptor(
       int num_arguments,
       const Array& optional_arguments_names);
 
  private:
+  // Forward declarations.
+  class DescriptorList;
+
+  DescriptorList* pc_descriptors_list_;
   DISALLOW_IMPLICIT_CONSTRUCTORS(CodeGenerator);
 };
 
 }  // namespace dart
 
 #endif  // VM_CODE_GENERATOR_ARM_H_