Make x64 to use the RecordWrite stub. This is a step towards getting

src/ia32/assembler-ia32.h

Index: src/ia32/assembler-ia32.h
===================================================================
--- src/ia32/assembler-ia32.h	(revision 8207)
+++ src/ia32/assembler-ia32.h	(working copy)
@@ -1016,18 +1016,6 @@
 
   int pc_offset() const { return pc_ - buffer_; }
 
-  // Used for patching the code stream while it is being emitted.
-  inline byte get_opcode(int offset) {
-    ASSERT(offset < 0);
-    ASSERT(pc_ + offset >= buffer_);
-    return pc_[offset];
-  }
-  inline void set_opcode(int offset, byte opcode) {
-    ASSERT(offset < 0);
-    ASSERT(pc_ + offset >= buffer_);
-    pc_[offset] = opcode;
-  }
-
   // Check if there is less than kGap bytes available in the buffer.
   // If this is the case, we need to grow the buffer before emitting
   // an instruction or relocation information.
@@ -1048,6 +1036,9 @@
   static const int kMaximalBufferSize = 512*MB;
   static const int kMinimalBufferSize = 4*KB;
 
+  byte byte_at(int pos)  { return buffer_[pos]; }
+  void set_byte_at(int pos, byte value) { buffer_[pos] = value; }
+
  protected:
   bool emit_debug_code() const { return emit_debug_code_; }
 
@@ -1062,8 +1053,6 @@
 
 
  private:
-  byte byte_at(int pos)  { return buffer_[pos]; }
-  void set_byte_at(int pos, byte value) { buffer_[pos] = value; }
   uint32_t long_at(int pos)  {
     return *reinterpret_cast<uint32_t*>(addr_at(pos));
   }