ES6 symbols: Allow symbols as property names

src/x64/macro-assembler-x64.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 904 matching lines @@
 
   // Check if the object in register heap_object is a string. Afterwards the
   // register map contains the object map and the register instance_type
   // contains the instance_type. The registers map and instance_type can be the
   // same in which case it contains the instance type afterwards. Either of the
   // registers map and instance_type can be the same as heap_object.
   Condition IsObjectStringType(Register heap_object,
                                Register map,
                                Register instance_type);
 
+  // Check if the object in register heap_object is a name. Afterwards the
+  // register map contains the object map and the register instance_type
+  // contains the instance_type. The registers map and instance_type can be the
+  // same in which case it contains the instance type afterwards. Either of the
+  // registers map and instance_type can be the same as heap_object.
+  Condition IsObjectNameType(Register heap_object,
+                             Register map,
+                             Register instance_type);
+
   // FCmp compares and pops the two values on top of the FPU stack.
   // The flag results are similar to integer cmp, but requires unsigned
   // jcc instructions (je, ja, jae, jb, jbe, je, and jz).
   void FCmp();
 
   void ClampUint8(Register reg);
 
   void ClampDoubleToUint8(XMMRegister input_reg,
                           XMMRegister temp_xmm_reg,
                           Register result_reg);
@@ skipping 23 matching lines @@
   void AssertSmi(Register object);
   void AssertSmi(const Operand& object);
 
   // Abort execution if a 64 bit register containing a 32 bit payload does not
   // have zeros in the top 32 bits, enabled via --debug-code.
   void AssertZeroExtended(Register reg);
 
   // Abort execution if argument is not a string, enabled via --debug-code.
   void AssertString(Register object);
 
+  // Abort execution if argument is not a name, enabled via --debug-code.
+  void AssertName(Register object);
+
   // Abort execution if argument is not the root value with the given index,
   // enabled via --debug-code.
   void AssertRootValue(Register src,
                        Heap::RootListIndex root_value_index,
                        const char* message);
 
   // ---------------------------------------------------------------------------
   // Exception handling
 
   // Push a new try handler and link it into try handler chain.
@@ skipping 515 matching lines @@
     masm->popfq();                                                           \
   }                                                                          \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_MACRO_ASSEMBLER_X64_H_