Fix jlh gdb macro.

R=franzih@chromium.org

Change-Id: I5f5ac245408c76a072f5cb3ae81b8773ddcd47cc
Reviewed-on: https://chromium-review.googlesource.com/808784Reviewed-by: Franziska Hinkelmann <franzih@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49912}

tools/gdbinit

@@ -13,7 +13,7 @@ end
 
 # Print v8::Local handle value.
 define jlh
-call _v8_internal_Print_Object(*(v8::internal::Object**)(*$arg0))
+call _v8_internal_Print_Object(*((v8::internal::Object**)($arg0).val_))
 end
 document jlh
 Print content of a v8::Local handle