RenderViewImpl gets either a main frame or a proxy frame routing id

So don't try to handle both anymore. DCHECK this is the case.

R=dcheng@chromium.org, piman@chromium.org

Bug: 720116, 419087
Change-Id: Ia10e77f6c81da37eacb1000ca679d1055b2ea372
Reviewed-on: https://chromium-review.googlesource.com/1239004Reviewed-by: Antoine Labour <piman@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594000}

content/renderer/render_view_impl.cc

@@ -534,6 +534,10 @@ void RenderViewImpl::Initialize(
 
   ApplyBlinkSettings(command_line, webview()->GetSettings());
 
+  // We have either a main frame or a proxy routing id.
+  DCHECK_NE(params->main_frame_routing_id != MSG_ROUTING_NONE,
+            params->proxy_routing_id != MSG_ROUTING_NONE);
+
   if (params->main_frame_routing_id != MSG_ROUTING_NONE) {
     CHECK(params->main_frame_interface_provider.is_valid());
     service_manager::mojom::InterfaceProviderPtr main_frame_interface_provider(
@@ -545,12 +549,9 @@ void RenderViewImpl::Initialize(
         GetWidget()->GetWebScreenInfo(), GetWidget()->compositor_deps(),
         opener_frame, params->devtools_main_frame_token,
         params->replicated_frame_state, params->has_committed_real_load);
-  }
 
-  // TODO(dcheng): Shouldn't these be mutually exclusive at this point? See
-  // https://crbug.com/720116 where the browser is apparently sending both
-  // routing IDs...
-  if (params->proxy_routing_id != MSG_ROUTING_NONE) {
+    main_render_frame_->Initialize();
+  } else {
     CHECK(params->swapped_out);
     RenderFrameProxy::CreateFrameProxy(params->proxy_routing_id, GetRoutingID(),
                                        opener_frame, MSG_ROUTING_NONE,
@@ -558,9 +559,6 @@ void RenderViewImpl::Initialize(
                                        params->devtools_main_frame_token);
   }
 
-  if (main_render_frame_)
-    main_render_frame_->Initialize();
-
   // If this RenderView's creation was initiated by an opener page in this
   // process, (e.g. window.open()), we won't be visible until we ask the opener,
   // via |show_callback|, to make us visible. Otherwise, we went through a