[Clean-up] Remove some dead code for handling Webstore sign-in.

chrome/browser/signin/signin_promo_unittest.cc

-// Copyright 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "chrome/browser/signin/signin_promo.h"
-
-#include "testing/gtest/include/gtest/gtest.h"
-#include "url/gurl.h"
-
-namespace signin {
-
-TEST(SigninPromoTest, GetNextPageURLForPromoURL_ValidContinueURL) {
-  GURL promo_url = GetPromoURLWithContinueURL(SOURCE_MENU,
-                                              false /* auto_close */,
-                                              false /* is_constrained */,
-                                              GURL("https://www.example.com"));
-  EXPECT_EQ(GURL("https://www.example.com"),
-            GetNextPageURLForPromoURL(promo_url));
-}
-
-TEST(SigninPromoTest, GetNextPageURLForPromoURL_EmptyContinueURL) {
-  GURL promo_url = GetPromoURLWithContinueURL(SOURCE_MENU,
-                                              false /* auto_close */,
-                                              false /* is_constrained */,
-                                              GURL());
-  EXPECT_TRUE(GetNextPageURLForPromoURL(promo_url).is_empty());
-}
-
-}  // namespace signin