Make the Isolate parameter mandatory in Locker and Unlocker classes.

src/debug.cc

Index: src/debug.cc
diff --git a/src/debug.cc b/src/debug.cc
index 1524349210a2e6d6e0c65e2978085950fffd6cb9..7baed884c295a4dec06f1b58ee9e29f26f876b86 100644
--- a/src/debug.cc
+++ b/src/debug.cc
@@ -3767,6 +3767,7 @@ void MessageDispatchHelperThread::Schedule() {
 
 
 void MessageDispatchHelperThread::Run() {
+  Isolate* isolate = Isolate::Current();
   while (true) {
     sem_->Wait();
     {
@@ -3774,8 +3775,8 @@ void MessageDispatchHelperThread::Run() {
       already_signalled_ = false;
     }
     {
-      Locker locker;
-      Isolate::Current()->debugger()->CallMessageDispatchHandler();
+      Locker locker(reinterpret_cast<v8::Isolate*>(isolate));
+      isolate->debugger()->CallMessageDispatchHandler();
     }
   }
 }