Add helper function to test that a given URL is a valid Gaia sign in URL.

google_apis/gaia/gaia_auth_util.cc

Index: google_apis/gaia/gaia_auth_util.cc
diff --git a/google_apis/gaia/gaia_auth_util.cc b/google_apis/gaia/gaia_auth_util.cc
index d8cac90d54ca2f2a71cbdef2c71ab012bc1ae7de..17fcae69bc469b1192ab04ad94d936593b17447c 100644
--- a/google_apis/gaia/gaia_auth_util.cc
+++ b/google_apis/gaia/gaia_auth_util.cc
@@ -9,6 +9,8 @@
 #include "base/logging.h"
 #include "base/string_split.h"
 #include "base/string_util.h"
+#include "google_apis/gaia/gaia_urls.h"
+#include "googleurl/src/gurl.h"
 
 namespace gaia {
 
@@ -58,4 +60,13 @@ std::string ExtractDomainName(const std::string& email_address) {
   return std::string();
 }
 
+bool IsGaiaSignonRealm(const GURL& url) {
+  if (!url.SchemeIsSecure())
+    return false;
+
+  // Also check "https://www.google.com" to support old style dasher logins.
+  return url == GURL(GaiaUrls::GetInstance()->gaia_origin_url()) ||
+      url == GURL("https://www.google.com/");
+}
+
 }  // namespace gaia