Add a blocking version of the sync promo dialog

chrome/browser/ui/webui/html_dialog_ui.cc

Index: chrome/browser/ui/webui/html_dialog_ui.cc
diff --git a/chrome/browser/ui/webui/html_dialog_ui.cc b/chrome/browser/ui/webui/html_dialog_ui.cc
index e89aed42f5cc34f9ee1b41a7b85047a544da2f55..eab52997dd4b65a743b8525e1da1705c2ab6d7b6 100644
--- a/chrome/browser/ui/webui/html_dialog_ui.cc
+++ b/chrome/browser/ui/webui/html_dialog_ui.cc
@@ -106,3 +106,19 @@ ExternalHtmlDialogUI::~ExternalHtmlDialogUI() {
 bool HtmlDialogUIDelegate::HandleContextMenu(const ContextMenuParams& params) {
   return false;
 }
+
+bool HtmlDialogUIDelegate::HandleOpenURLFromTab(
+    content::WebContents* source,
+    const content::OpenURLParams& params,
+    content::WebContents** out_new_contents) {
+  return false;
+}
+
+bool HtmlDialogUIDelegate::HandleAddNewContents(
+    content::WebContents* source,
+    content::WebContents* new_contents,
+    WindowOpenDisposition disposition,
+    const gfx::Rect& initial_pos,
+    bool user_gesture) {
+  return false;
+}