Clean up debugger flags.

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 600571e9d9351030f1802da38ff7bdc1eb434fce..d783d244129d58a8ce2eb1675764b114dd2adb4b 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -1421,7 +1421,7 @@ bool Genesis::CompileNative(Isolate* isolate,
                             Vector<const char> name,
                             Handle<String> source) {
   HandleScope scope(isolate);
-  isolate->debugger()->set_compiling_natives(true);
+  Debugger::IgnoreScope compiling_natives(isolate->debugger());
   // During genesis, the boilerplate for stack overflow won't work until the
   // environment has been at least partially initialized. Add a stack check
   // before entering JS code to catch overflow early.
@@ -1437,7 +1437,6 @@ bool Genesis::CompileNative(Isolate* isolate,
                                     true);
   ASSERT(isolate->has_pending_exception() != result);
   if (!result) isolate->clear_pending_exception();
-  isolate->debugger()->set_compiling_natives(false);
   return result;
 }