Bug 1465294 Part 1 - Always use the chrome tab group in middleman processes, r=smaug.

--HG--
extra : rebase_source : 608e3c225526b42e126293f068ed01a45f36432c

dom/base/TabGroup.cpp

@@ -120,6 +120,11 @@ TabGroup::GetFromActor(TabChild* aTabChild)
 {
   MOZ_RELEASE_ASSERT(NS_IsMainThread());
 
+  // Middleman processes do not assign event targets to their tab children.
+  if (recordreplay::IsMiddleman()) {
+    return GetChromeTabGroup();
+  }
+
   nsCOMPtr<nsIEventTarget> target = aTabChild->Manager()->GetEventTargetFor(aTabChild);
   if (!target) {
     return nullptr;