[d8] Fix LeakSanitizer failures on the bots due to ModuleEmbedderData

BUG=v8:1569
TBR=jochen@chromium.org

Review-Url: https://codereview.chromium.org/2403303002
Cr-Commit-Position: refs/heads/master@{#40143}

src/d8.cc

@@ -725,8 +725,12 @@ PerIsolateData::RealmScope::RealmScope(PerIsolateData* data) : data_(data) {
 
 PerIsolateData::RealmScope::~RealmScope() {
   // Drop realms to avoid keeping them alive.
-  for (int i = 0; i < data_->realm_count_; ++i)
-    data_->realms_[i].Reset();
+  for (int i = 0; i < data_->realm_count_; ++i) {
+    Global<Context>& realm = data_->realms_[i];
+    if (realm.IsEmpty()) continue;
+    DisposeModuleEmbedderData(realm.Get(data_->isolate_));
+    realm.Reset();
+  }
   delete[] data_->realms_;
   if (!data_->realm_shared_.IsEmpty())
     data_->realm_shared_.Reset();