Add bit_field3 to Map objects

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index d7d5af3bd33e704bc2c07291c33edef6d8b0fa70..978fa0d447ea253275cceb7d7e88b39f78053a14 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -782,6 +782,8 @@ class MacroAssembler: public Assembler {
                           Register result_reg,
                           Register temp_reg);
 
+  void LoadInstanceDescriptors(Register map, Register descriptors);
+
   // Abort execution if argument is not a number. Used in debug code.
   void AbortIfNotNumber(Register object);