Update NewTabPage for ephemeral Guest profiles.

Guest NTP is now shown for ephemeral Guest profiles.

This change is behind disabled EnableEphemeralGuestProfilesOnDesktop
flag. Please see go/guest-on-disk for more context.

Bug: 1125474
Change-Id: I1b2e8f727f92c10d561e630ac7bce61b5d4eef94
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2452731
Commit-Queue: Ramin Halavati <rhalavati@chromium.org>
Reviewed-by: Moe Ahmadi <mahmadi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814564}

chrome/browser/search/search.cc

@@ -172,9 +172,11 @@ struct NewTabURLDetails {
       : url(url), state(state) {}
 
   static NewTabURLDetails ForProfile(Profile* profile) {
-    // Incognito has its own New Tab.
-    if (profile->IsOffTheRecord())
+    // Incognito and Guest profiles have their own New Tab.
+    if (profile->IsIncognitoProfile() || profile->IsGuestSession() ||
+        profile->IsEphemeralGuestProfile()) {
       return NewTabURLDetails(GURL(), NEW_TAB_URL_INCOGNITO);
+    }
 
 #if defined(OS_ANDROID)
     const GURL local_url(chrome::kChromeSearchLocalNtpUrl);

chrome/browser/ui/webui/ntp/new_tab_ui.cc

@@ -58,7 +58,7 @@ NewTabUI::NewTabUI(content::WebUI* web_ui) : content::WebUIController(web_ui) {
 
   Profile* profile = GetProfile();
 
-  if (!profile->IsGuestSession()) {
+  if (!profile->IsGuestSession() && !profile->IsEphemeralGuestProfile()) {
     web_ui->AddMessageHandler(std::make_unique<ThemeHandler>());
     if (profile->IsOffTheRecord()) {
       web_ui->AddMessageHandler(

chrome/browser/ui/webui/ntp/ntp_resource_cache.cc

@@ -200,7 +200,7 @@ bool NTPResourceCache::NewTabHTMLNeedsRefresh() {
 
 NTPResourceCache::WindowType NTPResourceCache::GetWindowType(
     Profile* profile, content::RenderProcessHost* render_host) {
-  if (profile->IsGuestSession()) {
+  if (profile->IsGuestSession() || profile->IsEphemeralGuestProfile()) {
     return GUEST;
   } else if (render_host) {
     // Sometimes the |profile| is the parent (non-incognito) version of the user