Don't create debug context if debug listener is not set

test/cctest/test-debug.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 6907 matching lines @@
   v8::HandleScope scope(CcTest::isolate());
   v8::Debug::SetDebugEventListener(DebugEventBreakPointHitCount);
   v8::Local<v8::Context> context1 = v8::Debug::GetDebugContext();
   v8::Local<v8::Context> context2 = v8::Debug::GetDebugContext();
   CHECK(v8::Utils::OpenHandle(*context1).is_identical_to(
             v8::Utils::OpenHandle(*context2)));
   v8::Debug::SetDebugEventListener(NULL);
 }
 
 
+TEST(NoDebugContextWhenDebuggerDisabled) {
+  v8::HandleScope scope(CcTest::isolate());
+  v8::Local<v8::Context> context = v8::Debug::GetDebugContext();
+  CHECK(context.IsEmpty());
+}
+
+
 static v8::Handle<v8::Value> expected_callback_data;
 static void DebugEventContextChecker(const v8::Debug::EventDetails& details) {
   CHECK(details.GetEventContext() == expected_context);
   CHECK(expected_callback_data->Equals(details.GetCallbackData()));
 }
 
 
 // Check that event details contain context where debug event occured.
 TEST(DebugEventContext) {
   v8::Isolate* isolate = CcTest::isolate();
@@ skipping 655 matching lines @@
       "let y = 2;               \n"
       "debugger;                \n"
       "x * y",
       30);
   ExpectInt32(
       "x = 1; y = 2; \n"
       "debugger;"
       "x * y",
       30);
 }