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 f7fac34905f789c96ce28d0107dca525986da7ce..42da742d0cf2e4ca046510e8c48dc54234ebc22d 100644
--- a/chrome/browser/ui/startup/startup_browser_creator.cc
+++ b/chrome/browser/ui/startup/startup_browser_creator.cc
@@ -106,6 +106,12 @@ using content::ChildProcessSecurityPolicy;
 
 namespace {
 
+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;
+
 // Keeps track on which profiles have been launched.
 class ProfileLaunchObserver : public content::NotificationObserver {
  public:
@@ -446,6 +452,31 @@ void StartupBrowserCreator::RegisterLocalStatePrefs(
 }
 
 // static
+bool StartupBrowserCreator::SetDefaultBrowserCallback(
+    const base::Closure& callback) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  if (!g_default_browser_callback) {
+    g_default_browser_callback = new base::Closure(callback);

[Peter Kasting, 2015/09/25 20:52:27]

Nit: I might add a comment here on why this can't leak.

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

Done.

+    return true;
+  }
+  return false;
+}
+
+// static
+void StartupBrowserCreator::ClearDefaultBrowserCallback() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  if (g_default_browser_callback) {

[grt (UTC plus 2), 2015/09/28 14:31:04]

delete null is well-defined in C++, so you could remove this if() and
unconditionally do the delete and assignment. otherwise, one can imagine that
this code (which is only expected to be called when g_default_browser_callback
isn't null) will actually do two null checks on every call.

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

Done.

+    delete g_default_browser_callback;
+    g_default_browser_callback = nullptr;
+  }
+}
+
+// static
+const wchar_t* StartupBrowserCreator::GetDefaultBrowserUrl() {
+  return kSetDefaultBrowserHelpUrl;
+}
+
+// static
 std::vector<GURL> StartupBrowserCreator::GetURLsFromCommandLine(
     const base::CommandLine& command_line,
     const base::FilePath& cur_dir,
@@ -511,6 +542,7 @@ 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);
@@ -650,12 +682,25 @@ 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 :