Reland "Use the same browser instance in the sync confirmation dialog.

chrome/browser/ui/webui/signin/sync_confirmation_ui.cc

Index: chrome/browser/ui/webui/signin/sync_confirmation_ui.cc
diff --git a/chrome/browser/ui/webui/signin/sync_confirmation_ui.cc b/chrome/browser/ui/webui/signin/sync_confirmation_ui.cc
index d765bf1519b43a5104b248c85755b6db8bd81aef..e4525b912c0bd2a02258f95958d113c048595382 100644
--- a/chrome/browser/ui/webui/signin/sync_confirmation_ui.cc
+++ b/chrome/browser/ui/webui/signin/sync_confirmation_ui.cc
@@ -17,11 +17,6 @@
 #include "ui/base/webui/web_ui_util.h"
 
 SyncConfirmationUI::SyncConfirmationUI(content::WebUI* web_ui)
-    : SyncConfirmationUI(web_ui, base::MakeUnique<SyncConfirmationHandler>()) {}
-
-SyncConfirmationUI::SyncConfirmationUI(
-    content::WebUI* web_ui,
-    std::unique_ptr<SyncConfirmationHandler> handler)
     : WebDialogUI(web_ui) {
   Profile* profile = Profile::FromWebUI(web_ui);
   bool is_sync_allowed = profile->IsSyncAllowed();
@@ -67,5 +62,9 @@ SyncConfirmationUI::SyncConfirmationUI(
   source->AddLocalizedStrings(strings);
 
   content::WebUIDataSource::Add(profile, source);
-  web_ui->AddMessageHandler(std::move(handler));
+}
+
+void SyncConfirmationUI::InitializeMessageHandlerWithBrowser(Browser* browser) {
+  web_ui()->AddMessageHandler(
+      base::MakeUnique<SyncConfirmationHandler>(browser));
 }