Do not enter the debugger when debugger is not active.

src/execution.cc

 // 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 814 matching lines @@
   // Just continue if breaks are disabled.
   if (isolate->debug()->disable_break()) {
     return isolate->heap()->undefined_value();
   }
 
   // Ignore debug break during bootstrapping.
   if (isolate->bootstrapper()->IsActive()) {
     return isolate->heap()->undefined_value();
   }
 
+  // Ignore debug break if debugger is not active.
+  if (!isolate->debugger()->IsDebuggerActive()) {
+    return isolate->heap()->undefined_value();
+  }
+
   StackLimitCheck check(isolate);
   if (check.HasOverflowed()) {
     return isolate->heap()->undefined_value();
   }
 
   {
     JavaScriptFrameIterator it(isolate);
     ASSERT(!it.done());
     Object* fun = it.frame()->function();
     if (fun && fun->IsJSFunction()) {
@@ skipping 81 matching lines @@
   }
   if (stack_guard->IsInterrupted()) {
     stack_guard->Continue(INTERRUPT);
     return isolate->StackOverflow();
   }
   return isolate->heap()->undefined_value();
 }
 
 
 } }  // namespace v8::internal