[win] Fallback to registry when finding external handlers for a protocol

chrome/browser/shell_integration_win.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/shell_integration_win.h"
 
 #include <windows.h>
 #include <shlwapi.h>
 #include <shobjidl.h>
 #include <propkey.h>  // Needs to come after shobjidl.h.
@@ skipping 503 matching lines @@
   // Windows 8 and 10 both introduced a new way to set the default web client
   // which require user interaction.
   return SET_DEFAULT_INTERACTIVE;
 }
 
 bool IsElevationNeededForSettingDefaultProtocolClient() {
   return base::win::GetVersion() < base::win::VERSION_WIN8;
 }
 
 base::string16 GetApplicationNameForProtocol(const GURL& url) {
-  // Windows 8 or above requires a new protocol association query.
-  if (base::win::GetVersion() >= base::win::VERSION_WIN8)
-    return GetAppForProtocolUsingAssocQuery(url);
-  else
-    return GetAppForProtocolUsingRegistry(url);
+  base::string16 application_name;
+  // Windows 8 or above has a new protocol association query.
+  if (base::win::GetVersion() >= base::win::VERSION_WIN8) {
+    application_name = GetAppForProtocolUsingAssocQuery(url);
+    if (!application_name.empty())
+      return application_name;
+  }
+
+  return GetAppForProtocolUsingRegistry(url);
 }
 
 DefaultWebClientState GetDefaultBrowser() {
   return GetDefaultWebClientStateFromShellUtilDefaultState(
       ShellUtil::GetChromeDefaultState());
 }
 
 // There is no reliable way to say which browser is default on a machine (each
 // browser can have some of the protocols/shortcuts). So we look for only HTTP
 // protocol handler. Even this handler is located at different places in
@@ skipping 310 matching lines @@
     if (base::PathExists(shortcut))
       return shortcut;
   }
 
   return base::FilePath();
 }
 
 }  // namespace win
 
 }  // namespace shell_integration