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

src/arm/simulator-arm.h

Index: src/arm/simulator-arm.h
diff --git a/src/arm/simulator-arm.h b/src/arm/simulator-arm.h
index 391ef69f5efd62b213a7d14ab515c3feefbfe544..585f1e01767cb3f2ef66f6a2295e2293bc57dc3d 100644
--- a/src/arm/simulator-arm.h
+++ b/src/arm/simulator-arm.h
@@ -194,6 +194,10 @@ class Simulator {
   // 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);
@@ -360,6 +364,9 @@ class Simulator {
   bool pc_modified_;
   int icount_;
 
+  // Debugger input.
+  char* last_debugger_input_;
+
   // Icache simulation
   v8::internal::HashMap* i_cache_;