Get rid of a useless helper method in the register allocator.

src/lithium.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 43 matching lines @@
   int index() const { return static_cast<int>(value_) >> kKindFieldWidth; }
   bool IsConstantOperand() const { return kind() == CONSTANT_OPERAND; }
   bool IsStackSlot() const { return kind() == STACK_SLOT; }
   bool IsDoubleStackSlot() const { return kind() == DOUBLE_STACK_SLOT; }
   bool IsRegister() const { return kind() == REGISTER; }
   bool IsDoubleRegister() const { return kind() == DOUBLE_REGISTER; }
   bool IsArgument() const { return kind() == ARGUMENT; }
   bool IsUnallocated() const { return kind() == UNALLOCATED; }
   bool IsIgnored() const { return kind() == INVALID; }
   bool Equals(LOperand* other) const { return value_ == other->value_; }
-  int VirtualRegister();
 
   void PrintTo(StringStream* stream);
   void ConvertTo(Kind kind, int index) {
     value_ = KindField::encode(kind);
     value_ |= index << kKindFieldWidth;
     ASSERT(this->index() == index);
   }
 
  protected:
   static const int kKindFieldWidth = 3;
@@ skipping 87 matching lines @@
     return policy() == SAME_AS_FIRST_INPUT;
   }
   Policy policy() const { return PolicyField::decode(value_); }
   void set_policy(Policy policy) {
     value_ = PolicyField::update(value_, policy);
   }
   int fixed_index() const {
     return static_cast<int>(value_) >> kFixedIndexShift;
   }
 
-  unsigned virtual_register() const {
+  int virtual_register() const {
     return VirtualRegisterField::decode(value_);
   }
 
   void set_virtual_register(unsigned id) {
     value_ = VirtualRegisterField::update(value_, id);
   }
 
   LUnallocated* CopyUnconstrained() {
     LUnallocated* result = new LUnallocated(ANY);
     result->set_virtual_register(virtual_register());
@@ skipping 417 matching lines @@
   ShallowIterator current_iterator_;
 };
 
 
 int ElementsKindToShiftSize(ElementsKind elements_kind);
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_LITHIUM_H_