[NTP] Only show custom background on Google NTP

Custom backgrounds should only be applied when Google is set
as the search provider. Adds ApplyGoogleNtpThemeElements to
set/unset the background as needed.

Bug: 851290
Change-Id: I2fa7ca1081df818b455df27d1496047b0a800765
Reviewed-on: https://chromium-review.googlesource.com/1112379Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Kyle Milka <kmilka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#570051}

chrome/browser/search/instant_service.cc

@@ -146,11 +146,14 @@ void InstantService::UndoAllMostVisitedDeletions() {
   }
 }
 
-void InstantService::UpdateThemeInfo(bool force_update) {
+void InstantService::UpdateThemeInfo() {
   // Initialize |theme_info_| if necessary.
-  if (!theme_info_ || force_update) {
+  if (!theme_info_) {
     BuildThemeInfo();
   }
+
+  ApplyGoogleNtpThemeElements();
+
   NotifyAboutThemeInfo();
 }
 
@@ -175,7 +178,7 @@ void InstantService::SetCustomBackgroundURL(const GURL& url) {
     pref_service_->SetString(prefs::kNTPCustomBackgroundURL, url.spec());
   }
 
-  UpdateThemeInfo(true);
+  UpdateThemeInfo();
 }
 
 void InstantService::Shutdown() {
@@ -359,12 +362,17 @@ void InstantService::BuildThemeInfo() {
     theme_info_->has_attribution =
         theme_provider.HasCustomImage(IDR_THEME_NTP_ATTRIBUTION);
   }
+}
 
+void InstantService::ApplyGoogleNtpThemeElements() {
   // User has set a custom background image.
   GURL custom_background_url(
       profile_->GetPrefs()->GetString(prefs::kNTPCustomBackgroundURL));
-  if (custom_background_url.is_valid()) {
+  if (custom_background_url.is_valid() &&
+      search::DefaultSearchProviderIsGoogle(profile_)) {
     theme_info_->custom_background_url = custom_background_url;
+  } else {
+    theme_info_->custom_background_url = GURL::EmptyGURL();
   }
 }
 

chrome/browser/search/instant_service.h

@@ -85,7 +85,7 @@ class InstantService : public KeyedService,
   //
   // TODO(kmadhusu): Invoking this from InstantController shouldn't be
   // necessary. Investigate more and remove this from here.
-  void UpdateThemeInfo(bool force_update);
+  void UpdateThemeInfo();
 
   // Invoked by the InstantController to update most visited items details for
   // NTP.
@@ -126,6 +126,8 @@ class InstantService : public KeyedService,
 
   void BuildThemeInfo();
 
+  void ApplyGoogleNtpThemeElements();
+
   Profile* const profile_;
 
   // The process ids associated with Instant processes.

chrome/browser/ui/search/instant_controller.cc

@@ -93,7 +93,7 @@ void InstantController::UpdateInfoForInstantTab() {
   InstantService* instant_service =
       InstantServiceFactory::GetForProfile(profile_);
   if (instant_service) {
-    instant_service->UpdateThemeInfo(false);
+    instant_service->UpdateThemeInfo();
     instant_service->UpdateMostVisitedItemsInfo();
   }
 }