Canary versions no longer always remove protocol handlers at startup.

chrome/browser/custom_handlers/protocol_handler_registry.cc

 // Copyright (c) 2011 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/custom_handlers/protocol_handler_registry.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/logging.h"
@@ skipping 156 matching lines @@
 // registration for a protocol is no longer Chrome.
 bool ShouldRemoveHandlersNotInOS() {
 #if defined(OS_LINUX)
   // We don't do this on Linux as the OS registration there is not reliable,
   // and Chrome OS doesn't have any notion of OS registration.
   // TODO(benwells): When Linux support is more reliable remove this
   // difference (http://crbug.com/88255).
   return false;
 #else
   const CommandLine& cmd_line = *CommandLine::ForCurrentProcess();
-  return !cmd_line.HasSwitch(switches::kDisableCustomProtocolOSCheck);
+  return ShellIntegration::CanSetAsDefaultProtocolClient() &&
+      !cmd_line.HasSwitch(switches::kDisableCustomProtocolOSCheck);
 #endif
 }
 
 } // namespace
 
 void ProtocolHandlerRegistry::Load() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   is_loading_ = true;
   PrefService* prefs = profile_->GetPrefs();
   if (prefs->HasPrefPath(prefs::kCustomHandlersEnabled)) {
@@ skipping 383 matching lines @@
       registry_->RemoveDefaultHandler(worker_->protocol());
   } else {
     NOTREACHED();
   }
 }
 
 void ProtocolHandlerRegistry::DefaultClientObserver::SetWorker(
     ShellIntegration::DefaultProtocolClientWorker* worker) {
   worker_ = worker;
 }