Clean up some uses of Failures and MaybeObjects.

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 1488 matching lines @@
   void LoadAllocationTopHelper(Register result,
                                Register scratch,
                                AllocationFlags flags);
 
   // Update allocation top with value in result_end register.
   // If scratch is valid, it contains the address of the allocation top.
   void UpdateAllocationTopHelper(Register result_end,
                                  Register scratch,
                                  AllocationFlags flags);
 
-  // Helper for PopHandleScope.  Allowed to perform a GC and returns
-  // NULL if gc_allowed.  Does not perform a GC if !gc_allowed, and
-  // possibly returns a failure object indicating an allocation failure.
-  Object* PopHandleScopeHelper(Register saved,
-                               Register scratch,
-                               bool gc_allowed);
-
   // Helper for implementing JumpIfNotInNewSpace and JumpIfInNewSpace.
   void InNewSpace(Register object,
                   Register scratch,
                   Condition cc,
                   Label* branch,
                   Label::Distance distance = Label::kFar);
 
   // Helper for finding the mark bits for an address.  Afterwards, the
   // bitmap register points at the word with the mark bits and the mask
   // the position of the first bit.  Uses rcx as scratch and leaves addr_reg
@@ skipping 98 matching lines @@
     masm->popfq();                                                           \
   }                                                                          \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_MACRO_ASSEMBLER_X64_H_