Repeat last debugger command in the arm simulator when command input is empty.

src/arm/simulator-arm.h

 // Copyright 2011 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 176 matching lines @@
   // generated RegExp code with 7 parameters. This is a convenience function,
   // which sets up the simulator state and grabs the result on return.
   int32_t Call(byte* entry, int argument_count, ...);
 
   // Push an address onto the JS stack.
   uintptr_t PushAddress(uintptr_t address);
 
   // Pop an address from the JS stack.
   uintptr_t PopAddress();
 
+  // Debugger input.
+  void set_last_debugger_input(char* input);
+  char* last_debugger_input() { return last_debugger_input_; }
+
   // ICache checking.
   static void FlushICache(v8::internal::HashMap* i_cache, void* start,
                           size_t size);
 
   // Returns true if pc register contains one of the 'special_values' defined
   // below (bad_lr, end_sim_pc).
   bool has_bad_pc() const;
 
   // EABI variant for double arguments in use.
   bool use_eabi_hardfloat() {
@@ skipping 146 matching lines @@
   bool div_zero_vfp_flag_;
   bool overflow_vfp_flag_;
   bool underflow_vfp_flag_;
   bool inexact_vfp_flag_;
 
   // Simulator support.
   char* stack_;
   bool pc_modified_;
   int icount_;
 
+  // Debugger input.
+  char* last_debugger_input_;
+
   // Icache simulation
   v8::internal::HashMap* i_cache_;
 
   // Registered breakpoints.
   Instruction* break_pc_;
   Instr break_instr_;
 
   v8::internal::Isolate* isolate_;
 
   // A stop is watched if its code is less than kNumOfWatchedStops.
@@ skipping 49 matching lines @@
 
   static inline void UnregisterCTryCatch() {
     Simulator::current(Isolate::Current())->PopAddress();
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // !defined(USE_SIMULATOR)
 #endif  // V8_ARM_SIMULATOR_ARM_H_