Add comment to use counter def, so it doesn't constantly get out of sync

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index 081b6c3810793b92dab625578727e46271689588..9dba9fd118bb492816768296665265d94ccf97e2 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -5469,6 +5469,9 @@ class V8_EXPORT Isolate {
     kHtmlComment = 21,
     kSloppyModeBlockScopedFunctionRedefinition = 22,
     kForInInitializer = 23,
+
+    // If you add new values here, you'll also need to update V8Initializer.cpp
+    // in Blink.

[adamk, 2016/02/17 18:56:26]

Maybe this should just say Chromium? Blink isn't really a codebase anymore, just
a project :)

     kUseCounterFeatureCount  // This enum value must be last.
   };