Setting chrome as the default browser is now fixed on Windows 10

chrome/browser/ui/startup/startup_browser_creator.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_STARTUP_STARTUP_BROWSER_CREATOR_H_
 #define CHROME_BROWSER_UI_STARTUP_STARTUP_BROWSER_CREATOR_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 85 matching lines @@
 
   bool show_main_browser_window() const {
     return show_main_browser_window_;
   }
 
   // For faking that no profiles have been launched yet.
   static void ClearLaunchedProfilesForTesting();
 
   static void RegisterLocalStatePrefs(PrefRegistrySimple* registry);
 
+#if defined(OS_WIN)
+  // Setting Chrome as the default browser in Windows 10+ requires a specific
+  // url to be opened through openwith.exe. This url is intercepted in
+  // ProcessCmdLineImpl when the callback is set. See DefaultBrowserWorker in
+  // shell_integration.h for more details. Only call this on the UI thread.
+  static bool SetDefaultBrowserCallback(const base::Closure& callback);

[grt (UTC plus 2), 2015/09/28 14:31:05]

please document the return value.

[Patrick Monette, 2015/09/28 23:46:38]

Done.

+
+  // Clears the callback when it isn't needed anymore. Only call this on the UI
+  // thread.
+  static void ClearDefaultBrowserCallback();
+
+  // Returns the url used to set Chrome as the default browser asynchronously.
+  static const wchar_t* GetDefaultBrowserUrl();
+#endif  // defined(OS_WIN)
+
  private:
   friend class CloudPrintProxyPolicyTest;
   friend class CloudPrintProxyPolicyStartupTest;
   friend class StartupBrowserCreatorImpl;
   FRIEND_TEST_ALL_PREFIXES(StartupBrowserCreatorTest,
                            ReadingWasRestartedAfterNormalStart);
   FRIEND_TEST_ALL_PREFIXES(StartupBrowserCreatorTest,
                            ReadingWasRestartedAfterRestart);
   FRIEND_TEST_ALL_PREFIXES(StartupBrowserCreatorTest, UpdateWithTwoProfiles);
   FRIEND_TEST_ALL_PREFIXES(StartupBrowserCreatorTest, LastUsedProfileActivated);
@@ skipping 58 matching lines @@
 // Returns true if |profile| has exited uncleanly and has not been launched
 // after the unclean exit.
 bool HasPendingUncleanExit(Profile* profile);
 
 // Returns the path that contains the profile that should be loaded on process
 // startup.
 base::FilePath GetStartupProfilePath(const base::FilePath& user_data_dir,
                                      const base::CommandLine& command_line);
 
 #endif  // CHROME_BROWSER_UI_STARTUP_STARTUP_BROWSER_CREATOR_H_