Implement Win 10 onboarding content logic

chrome/browser/shell_integration_win.cc

Index: chrome/browser/shell_integration_win.cc
diff --git a/chrome/browser/shell_integration_win.cc b/chrome/browser/shell_integration_win.cc
index fffcc9c46b1552a94d946b33cc37cec1c9a93233..e0f0837c84b155372dee6822eb24246e7fe5c23f 100644
--- a/chrome/browser/shell_integration_win.cc
+++ b/chrome/browser/shell_integration_win.cc
@@ -487,6 +487,9 @@ IsPinnedToTaskbarHelper::IsPinnedToTaskbarHelper(
           l10n_util::GetStringUTF16(IDS_UTILITY_PROCESS_SHELL_HANDLER_NAME)),
       error_callback_(error_callback),
       result_callback_(result_callback) {
+  DCHECK(error_callback);
+  DCHECK(result_callback);
+
   // |shell_handler_| owns the callbacks and is guaranteed to be destroyed
   // before |this|, therefore making base::Unretained() safe to use.
   shell_handler_.set_error_callback(base::Bind(