Fix handling of external protocols with PlzNavigate.

chrome/renderer/chrome_render_thread_observer.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 "chrome/renderer/chrome_render_thread_observer.h"
 
 #include <stddef.h>
 
 #include <limits>
 #include <memory>
@@ skipping 232 matching lines @@
   thread->GetInterfaceRegistry()->AddInterface(
       base::Bind(CreateResourceUsageReporter, weak_factory_.GetWeakPtr()));
 
   // Configure modules that need access to resources.
   net::NetModule::SetResourceProvider(chrome_common_net::NetResourceProvider);
   media::SetLocalizedStringProvider(
       chrome_common_media::LocalizedStringProvider);
 
   // chrome-native: is a scheme used for placeholder navigations that allow
   // UIs to be drawn with platform native widgets instead of HTML.  These pages
-  // should not be accessible, and should also be treated as empty documents
-  // that can commit synchronously.  No code should be runnable in these pages,
+  // should not be accessible.  No code should be runnable in these pages,
   // so it should not need to access anything nor should it allow javascript
   // URLs since it should never be visible to the user.
+  // See also ChromeContentClient::AddAdditionalSchemes that adds it as an
+  // empty document scheme.
   WebString native_scheme(WebString::fromASCII(chrome::kChromeNativeScheme));
   WebSecurityPolicy::registerURLSchemeAsDisplayIsolated(native_scheme);
-  WebSecurityPolicy::registerURLSchemeAsEmptyDocument(native_scheme);
   WebSecurityPolicy::registerURLSchemeAsNotAllowingJavascriptURLs(
       native_scheme);
 
   thread->GetInterfaceRegistry()->AddInterface(
       visited_link_slave_->GetBindCallback());
 }
 
 ChromeRenderThreadObserver::~ChromeRenderThreadObserver() {}
 
 void ChromeRenderThreadObserver::RegisterMojoInterfaces(
@@ skipping 34 matching lines @@
 
 void ChromeRenderThreadObserver::OnRendererConfigurationAssociatedRequest(
     chrome::mojom::RendererConfigurationAssociatedRequest request) {
   renderer_configuration_bindings_.AddBinding(this, std::move(request));
 }
 
 const RendererContentSettingRules*
 ChromeRenderThreadObserver::content_setting_rules() const {
   return &content_setting_rules_;
 }