Trigger debug event on not yet caught exception in promises.

include/v8-debug.h

Index: include/v8-debug.h
diff --git a/include/v8-debug.h b/include/v8-debug.h
index 49916fed662c565619d0f6cadf0a874f8905075d..6b2c27830cf4d1465ade64968c72bd92f6f29829 100644
--- a/include/v8-debug.h
+++ b/include/v8-debug.h
@@ -43,7 +43,8 @@ enum DebugEvent {
   BeforeCompile = 4,
   AfterCompile  = 5,
   ScriptCollected = 6,
-  BreakForCommand = 7
+  UncaughtExceptionInPromise = 7,
+  BreakForCommand = 8
 };