Remove null Document check from RenderFrameImpl::OnMessageReceived

content/renderer/render_frame_impl.cc

Index: content/renderer/render_frame_impl.cc
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index f68bb2e5666f71404361907fd889992464b5d5cf..68ad6f13d7d6404392bd7c7e668003f310b74dd4 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -1477,13 +1477,9 @@ bool RenderFrameImpl::OnMessageReceived(const IPC::Message& msg) {
   if (!frame_)
     return false;
 
-  // TODO(kenrb): document() should not be null, but as a transitional step
-  // we have RenderFrameProxy 'wrapping' a RenderFrameImpl, passing messages
-  // to this method. This happens for a top-level remote frame, where a
-  // document-less RenderFrame is replaced by a RenderFrameProxy but kept
-  // around and is still able to receive messages.
-  if (!frame_->document().isNull())
-    GetContentClient()->SetActiveURL(frame_->document().url());
+  DCHECK(!frame_->document().isNull());
+
+  GetContentClient()->SetActiveURL(frame_->document().url());
 
   for (auto& observer : observers_) {
     if (observer.OnMessageReceived(msg))