signin: force web signin flow initiated visits to accounts.google.com to their own process.

chrome/browser/ui/webui/sync_promo/sync_promo_ui.cc

Index: chrome/browser/ui/webui/sync_promo/sync_promo_ui.cc
diff --git a/chrome/browser/ui/webui/sync_promo/sync_promo_ui.cc b/chrome/browser/ui/webui/sync_promo/sync_promo_ui.cc
index 4c0920d235cedc0c7b9665202be3ad1614aaa0b5..32618801e8c7ca3bdec73692a6684eb5f72c2a6d 100644
--- a/chrome/browser/ui/webui/sync_promo/sync_promo_ui.cc
+++ b/chrome/browser/ui/webui/sync_promo/sync_promo_ui.cc
@@ -259,6 +259,18 @@ GURL SyncPromoUI::GetSyncPromoURL(const GURL& next_page,
 }
 
 // static
+bool SyncPromoUI::IsWebBasedSigninFlowURL(const GURL& url) {
+  if (url.SchemeIs(chrome::kChromeSigninScheme))
+    return true;
+
+  GURL service_login(GaiaUrls::GetInstance()->service_login_url());
+  if (url.GetOrigin() != service_login.GetOrigin())
+    return false;
+
+  return url.path() == service_login.path();
+}
+
+// static
 GURL SyncPromoUI::GetNextPageURLForSyncPromoURL(const GURL& url) {
   const char* key_name = UseWebBasedSigninFlow() ? kSyncPromoQueryKeyContinue :
       kSyncPromoQueryKeyNextPage;