[Presentation API] set presentation_receiver flag in offscreen tab

chrome/browser/extensions/api/tab_capture/offscreen_tab.cc

 // Copyright 2015 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 "chrome/browser/extensions/api/tab_capture/offscreen_tab.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "chrome/browser/extensions/api/tab_capture/tab_capture_registry.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/web_contents_sizer.h"
+#include "content/public/browser/render_view_host.h"
 #include "content/public/browser/render_widget_host_view.h"
 #include "content/public/browser/web_contents.h"
+#include "content/public/common/web_preferences.h"
 #include "extensions/browser/extension_host.h"
 #include "extensions/browser/process_manager.h"
 
 using content::WebContents;
 
 DEFINE_WEB_CONTENTS_USER_DATA_KEY(extensions::OffscreenTabsOwner);
 
 namespace {
 
 // Upper limit on the number of simultaneous off-screen tabs per extension
@@ skipping 86 matching lines @@
 
   // Mute audio output.  When tab capture starts, the audio will be
   // automatically unmuted, but will be captured into the MediaStream.
   offscreen_tab_web_contents_->SetAudioMuted(true);
 
   // TODO(imcheng): If |optional_presentation_id| is not empty, register it with
   // the PresentationRouter.  http://crbug.com/513859
   if (!optional_presentation_id.empty()) {
     NOTIMPLEMENTED()
         << "Register with PresentationRouter, id=" << optional_presentation_id;
+
+    if (auto* render_view_host =
+            offscreen_tab_web_contents_->GetRenderViewHost()) {
+      auto web_prefs = render_view_host->GetWebkitPreferences();
+      web_prefs.presentation_receiver = true;
+      render_view_host->UpdateWebkitPreferences(web_prefs);
+    }
   }
 
   // Navigate to the initial URL.
   content::NavigationController::LoadURLParams load_params(start_url_);
   load_params.should_replace_current_entry = true;
   load_params.should_clear_history_list = true;
   offscreen_tab_web_contents_->GetController().LoadURLWithParams(load_params);
 
   start_time_ = base::TimeTicks::Now();
   DieIfContentCaptureEnded();
@@ skipping 231 matching lines @@
 
   // Schedule the timer to check again in a second.
   capture_poll_timer_.Start(
       FROM_HERE,
       base::TimeDelta::FromSeconds(kPollIntervalInSeconds),
       base::Bind(&OffscreenTab::DieIfContentCaptureEnded,
                  base::Unretained(this)));
 }
 
 }  // namespace extensions