Let DelegateFrameHost in Mac and Android use correct FrameSinkId during creation

content/browser/renderer_host/render_widget_host_view_aura.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/render_widget_host_view_aura.h"
 
 #include <set>
 #include <utility>
 
 #include "base/auto_reset.h"
@@ skipping 1897 matching lines @@
       ui::mojom::kEmbedFlagEmbedderInterceptsEvents,
       base::Bind(&EmbedCallback));
 }
 
 void RenderWidgetHostViewAura::CreateDelegatedFrameHostClient() {
   if (IsMus())
     return;
 
   // GuestViews have two RenderWidgetHostViews and so we need to make sure
   // we don't have FrameSinkId collisions.
+  // The FrameSinkId generated here must be unique with FrameSinkId allocated
+  // in ContextFactoryPrivate.
+  // TODO(crbug.com/685777): Centralize allocation in one place for easier
+  // maintenance.
   ImageTransportFactory* factory = ImageTransportFactory::GetInstance();
   cc::FrameSinkId frame_sink_id =
       is_guest_view_hack_
           ? factory->GetContextFactoryPrivate()->AllocateFrameSinkId()
           : cc::FrameSinkId(
                 base::checked_cast<uint32_t>(host_->GetProcess()->GetID()),
                 base::checked_cast<uint32_t>(host_->GetRoutingID()));
   // Tests may set |delegated_frame_host_client_|.
   if (!delegated_frame_host_client_) {
     delegated_frame_host_client_ =
@@ skipping 446 matching lines @@
 
 void RenderWidgetHostViewAura::SetPopupChild(
     RenderWidgetHostViewAura* popup_child_host_view) {
   popup_child_host_view_ = popup_child_host_view;
   event_handler_->SetPopupChild(
       popup_child_host_view,
       popup_child_host_view ? popup_child_host_view->event_handler() : nullptr);
 }
 
 }  // namespace content