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

chrome/browser/ui/startup/startup_browser_creator.cc

Index: chrome/browser/ui/startup/startup_browser_creator.cc
diff --git a/chrome/browser/ui/startup/startup_browser_creator.cc b/chrome/browser/ui/startup/startup_browser_creator.cc
index f114fb6db5500558618a6e68b44da2bd89030703..8553942b943d4f7bf5f500458b1aae6baf8b4855 100644
--- a/chrome/browser/ui/startup/startup_browser_creator.cc
+++ b/chrome/browser/ui/startup/startup_browser_creator.cc
@@ -106,6 +106,14 @@ using content::ChildProcessSecurityPolicy;
 
 namespace {
 
+#if defined(OS_WIN)
+const wchar_t kSetDefaultBrowserHelpUrl[] =
+    L"https://support.google.com/chrome?p=default_browser";
+
+// Not thread-safe. Always use or modify this callback on the UI thread.
+base::Closure* g_default_browser_callback = nullptr;
+#endif  // defined(OS_WIN)
+
 // Keeps track on which profiles have been launched.
 class ProfileLaunchObserver : public content::NotificationObserver {
  public:
@@ -484,6 +492,34 @@ void StartupBrowserCreator::RegisterLocalStatePrefs(
 #endif
 }
 
+
+#if defined(OS_WIN)
+// static
+bool StartupBrowserCreator::SetDefaultBrowserCallback(
+    const base::Closure& callback) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  if (!g_default_browser_callback) {
+    // This won't leak because the worker class invoking this function always
+    // calls ClearDefaultBrowserCallback() in its destructor.
+    g_default_browser_callback = new base::Closure(callback);
+    return true;
+  }
+  return false;
+}
+
+// static
+void StartupBrowserCreator::ClearDefaultBrowserCallback() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  delete g_default_browser_callback;
+  g_default_browser_callback = nullptr;
+}
+
+// static
+const wchar_t* StartupBrowserCreator::GetDefaultBrowserUrl() {
+  return kSetDefaultBrowserHelpUrl;
+}
+#endif  // defined(OS_WIN)
+
 // static
 std::vector<GURL> StartupBrowserCreator::GetURLsFromCommandLine(
     const base::CommandLine& command_line,
@@ -550,6 +586,7 @@ bool StartupBrowserCreator::ProcessCmdLineImpl(
     Profile* last_used_profile,
     const Profiles& last_opened_profiles,
     StartupBrowserCreator* browser_creator) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
   TRACE_EVENT0("startup", "StartupBrowserCreator::ProcessCmdLineImpl");
 
   DCHECK(last_used_profile);
@@ -689,12 +726,25 @@ bool StartupBrowserCreator::ProcessCmdLineImpl(
   }
 
 #if defined(OS_WIN)
+  // Intercept a specific url when setting the default browser asynchronously.
+  // This only happens on Windows 10+.
+  if (g_default_browser_callback) {
+    base::CommandLine::StringType default_browser_url_(
+        kSetDefaultBrowserHelpUrl);
+    for (const auto& arg : command_line.GetArgs()) {
+      if (arg == default_browser_url_) {
+        g_default_browser_callback->Run();
+        return true;
+      }
+    }
+  }
+
   // Log whether this process was a result of an action in the Windows Jumplist.
   if (command_line.HasSwitch(switches::kWinJumplistAction)) {
     jumplist::LogJumplistActionFromSwitchValue(
         command_line.GetSwitchValueASCII(switches::kWinJumplistAction));
   }
-#endif
+#endif  // defined(OS_WIN)
 
   chrome::startup::IsProcessStartup is_process_startup = process_startup ?
       chrome::startup::IS_PROCESS_STARTUP :