Revert "WebUI NTP: redirect sign-in to chrome://newtab"

This reverts commit 142274a8.

Reason for revert: Consistent test failures in https://ci.chromium.org/p/chromium/builders/ci/Network%20Service%20Linux

It looks like EnableSyncAfterToken also needs an updated GURL.

Original change's description:
> WebUI NTP: redirect sign-in to chrome://newtab
> 
> Bug: 1015293
> Change-Id: Ic76e7911403a925fa46a5b5fc58eca95fa292269
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2209392
> Commit-Queue: Tibor Goldschwendt <tiborg@chromium.org>
> Reviewed-by: Lei Zhang <thestig@chromium.org>
> Reviewed-by: Tibor Goldschwendt <tiborg@chromium.org>
> Auto-Submit: Esmael Elmoslimany <aee@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#771116}

TBR=droger@chromium.org,thestig@chromium.org,tiborg@chromium.org,aee@chromium.org

Change-Id: Ia5700a01efee9ee198cb5615fd59232ba481402f
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1015293
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2212809Reviewed-by: Ramya Nagarajan <ramyan@chromium.org>
Commit-Queue: Ramya Nagarajan <ramyan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#771179}

chrome/browser/signin/dice_browsertest.cc

@@ -934,7 +934,7 @@ IN_PROC_BROWSER_TEST_F(DiceBrowserTest, MAYBE_EnableSyncBeforeToken) {
             dice_request_header_);
 
   ui_test_utils::UrlLoadObserver ntp_url_observer(
-      GURL(chrome::kChromeUINewTabURL),
+      GURL(chrome::kChromeSearchLocalNtpUrl),
       content::NotificationService::AllSources());
 
   WaitForSigninSucceeded();

chrome/browser/signin/process_dice_header_delegate_impl.cc

@@ -24,7 +24,7 @@ namespace {
 void RedirectToNtp(content::WebContents* contents) {
   VLOG(1) << "RedirectToNtp";
   contents->GetController().LoadURL(
-      GURL(chrome::kChromeUINewTabURL), content::Referrer(),
+      GURL(chrome::kChromeSearchLocalNtpUrl), content::Referrer(),
       ui::PAGE_TRANSITION_AUTO_TOPLEVEL, std::string());
 }
 

chrome/browser/signin/process_dice_header_delegate_impl_unittest.cc

@@ -240,8 +240,9 @@ TEST_P(ProcessDiceHeaderDelegateImplTestEnableSync, EnableSync) {
       CreateDelegateAndNavigateToSignin(GetParam().signin_tab);
   delegate->EnableSync(account_id_);
   EXPECT_EQ(GetParam().callback_called, enable_sync_called_);
-  GURL expected_url =
-      GetParam().show_ntp ? GURL(chrome::kChromeUINewTabURL) : signin_url_;
+  GURL expected_url = GetParam().show_ntp
+                          ? GURL(chrome::kChromeSearchLocalNtpUrl)
+                          : signin_url_;
   EXPECT_EQ(expected_url, web_contents()->GetVisibleURL());
   EXPECT_FALSE(show_error_called_);
   // Check that the sync signin flow is complete.
@@ -282,8 +283,9 @@ TEST_P(ProcessDiceHeaderDelegateImplTestHandleTokenExchangeFailure,
   delegate->HandleTokenExchangeFailure(email_, auth_error_);
   EXPECT_FALSE(enable_sync_called_);
   EXPECT_EQ(GetParam().callback_called, show_error_called_);
-  GURL expected_url =
-      GetParam().show_ntp ? GURL(chrome::kChromeUINewTabURL) : signin_url_;
+  GURL expected_url = GetParam().show_ntp
+                          ? GURL(chrome::kChromeSearchLocalNtpUrl)
+                          : signin_url_;
   EXPECT_EQ(expected_url, web_contents()->GetVisibleURL());
   // Check that the sync signin flow is complete.
   if (GetParam().signin_tab) {