src: use global SealHandleScope

Helps to find Handle leaks in Debug mode.

Ref: a5244d3 "deps: backport 1f8555 from v8's upstream"

PR-URL: https://github.com/nodejs/node/pull/3945
Reviewed-By: Fedor Indutny <fedor@indutny.com>
Reviewed-By: James Snell <jasnell@gmail.com>

src/node.cc

@@ -116,6 +116,7 @@ using v8::Number;
 using v8::Object;
 using v8::ObjectTemplate;
 using v8::PropertyCallbackInfo;
+using v8::SealHandleScope;
 using v8::String;
 using v8::TryCatch;
 using v8::Uint32;
@@ -3769,6 +3770,8 @@ int Start(int argc, char** argv) {
     if (use_debug_agent)
       EnableDebug(env);
 
+    {
+      SealHandleScope seal(node_isolate);
       bool more;
       do {
         more = uv_run(env->event_loop(), UV_RUN_ONCE);
@@ -3782,6 +3785,8 @@ int Start(int argc, char** argv) {
             more = true;
         }
       } while (more == true);
+    }
+
     code = EmitExit(env);
     RunAtExit(env);