Fixes the interactive default browser UX for policy setting

chrome/browser/external_protocol/external_protocol_handler.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/browser/external_protocol/external_protocol_handler.h"
 
 #include <stddef.h>
 
 #include <set>
 
@@ skipping 20 matching lines @@
 using content::BrowserThread;
 
 // Whether we accept requests for launching external protocols. This is set to
 // false every time an external protocol is requested, and set back to true on
 // each user gesture. This variable should only be accessed from the UI thread.
 static bool g_accept_requests = true;
 
 namespace {
 
 // Functions enabling unit testing. Using a NULL delegate will use the default
 // behavior; if a delegate is provided it will be used instead.

[grt (UTC plus 2), 2016/02/03 15:39:56]

please add something like:
// Ownership of |observer| is passed to the new worker.

[Patrick Monette, 2016/02/03 23:01:38]

Done.

 ShellIntegration::DefaultProtocolClientWorker* CreateShellWorker(
     ShellIntegration::DefaultWebClientObserver* observer,
     const std::string& protocol,
     ExternalProtocolHandler::Delegate* delegate) {
   if (!delegate)
-    return new ShellIntegration::DefaultProtocolClientWorker(observer,
-                                                             protocol);
+    return new ShellIntegration::DefaultProtocolClientWorker(observer, protocol,
+                                                             true);
 
   return delegate->CreateShellWorker(observer, protocol);
 }
 
 ExternalProtocolHandler::BlockState GetBlockStateWithDelegate(
     const std::string& scheme,
     ExternalProtocolHandler::Delegate* delegate) {
   if (!delegate)
     return ExternalProtocolHandler::GetBlockState(scheme);
 
@@ skipping 80 matching lines @@
       RunExternalProtocolDialogWithDelegate(
           escaped_url_, render_process_host_id_, tab_contents_id_,
           page_transition_, has_user_gesture_, delegate_);
       return;
     }
 
     LaunchUrlWithoutSecurityCheckWithDelegate(
         escaped_url_, render_process_host_id_, tab_contents_id_, delegate_);
   }
 
-  bool IsOwnedByWorker() override { return true; }
-
  private:
   ExternalProtocolHandler::Delegate* delegate_;
   const GURL escaped_url_;
   const int render_process_host_id_;
   const int tab_contents_id_;
   const bool prompt_user_;
   const ui::PageTransition page_transition_;
   const bool has_user_gesture_;
 };
 
@@ skipping 164 matching lines @@
 // static
 void ExternalProtocolHandler::RegisterPrefs(PrefRegistrySimple* registry) {
   registry->RegisterDictionaryPref(prefs::kExcludedSchemes);
 }
 
 // static
 void ExternalProtocolHandler::PermitLaunchUrl() {
   DCHECK(base::MessageLoopForUI::IsCurrent());
   g_accept_requests = true;
 }