[NTP] Add ability to toggle between Most Visited and custom links

Implement toggleMostVisitedOrCustomLinks for the EmbbededSearchApi.
This will allow users to toggle between Most Visited tiles and custom
links.

Bug: 953822
Change-Id: Ide2d1a62456649a5b6f9ff45d16548ac1212e0b5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1572233Reviewed-by: Kyle Milka <kmilka@chromium.org>
Reviewed-by: Marc Treib <treib@chromium.org>
Reviewed-by: Greg Kerr <kerrnel@chromium.org>
Commit-Queue: Kristi Park <kristipark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652298}

chrome/browser/search/instant_service.cc

@@ -8,6 +8,7 @@
 #include <string>
 
 #include "base/bind.h"
+#include "base/callback.h"
 #include "base/files/file_util.h"
 #include "base/path_service.h"
 #include "base/scoped_observer.h"
@@ -120,7 +121,7 @@ class InstantService::SearchProviderObserver
     : public TemplateURLServiceObserver {
  public:
   explicit SearchProviderObserver(TemplateURLService* service,
-                                  base::RepeatingCallback<void(bool)> callback)
+                                  base::RepeatingClosure callback)
       : service_(service),
         is_google_(search::DefaultSearchProviderIsGoogle(service_)),
         callback_(std::move(callback)) {
@@ -138,7 +139,7 @@ class InstantService::SearchProviderObserver
  private:
   void OnTemplateURLServiceChanged() override {
     is_google_ = search::DefaultSearchProviderIsGoogle(service_);
-    callback_.Run(is_google_);
+    callback_.Run();
   }
 
   void OnTemplateURLServiceShuttingDown() override {
@@ -148,7 +149,7 @@ class InstantService::SearchProviderObserver
 
   TemplateURLService* service_;
   bool is_google_;
-  base::RepeatingCallback<void(bool)> callback_;
+  base::RepeatingClosure callback_;
 };
 
 InstantService::InstantService(Profile* profile)
@@ -173,8 +174,6 @@ InstantService::InstantService(Profile* profile)
 
   most_visited_sites_ = ChromeMostVisitedSitesFactory::NewForProfile(profile_);
   if (most_visited_sites_) {
-    bool custom_links_enabled = true;
-
     // Determine if we are using a third-party NTP. Custom links should only be
     // enabled for the default NTP.
     TemplateURLService* template_url_service =
@@ -184,13 +183,12 @@ InstantService::InstantService(Profile* profile)
           template_url_service,
           base::BindRepeating(&InstantService::OnSearchProviderChanged,
                               weak_ptr_factory_.GetWeakPtr()));
-      custom_links_enabled = search_provider_observer_->is_google();
     }
 
     // 9 tiles are required for the custom links feature in order to balance the
     // Most Visited rows (this is due to an additional "Add" button).
     most_visited_sites_->SetMostVisitedURLsObserver(this, 9);
-    most_visited_sites_->EnableCustomLinks(custom_links_enabled);
+    most_visited_sites_->EnableCustomLinks(IsCustomLinksEnabled());
   }
 
   if (profile_) {
@@ -282,50 +280,58 @@ void InstantService::UndoAllMostVisitedDeletions() {
   }
 }
 
-bool InstantService::AddCustomLink(const GURL& url, const std::string& title) {
-  if (most_visited_sites_)
-    return most_visited_sites_->AddCustomLink(url, base::UTF8ToUTF16(title));
+bool InstantService::ToggleMostVisitedOrCustomLinks() {
+  // Non-Google NTPs are not supported.
+  if (!most_visited_sites_ || !search_provider_observer_ ||
+      !search_provider_observer_->is_google()) {
     return false;
+  }
+  bool use_most_visited =
+      pref_service_->GetBoolean(prefs::kNtpUseMostVisitedTiles);
+  pref_service_->SetBoolean(prefs::kNtpUseMostVisitedTiles, !use_most_visited);
+  most_visited_sites_->EnableCustomLinks(IsCustomLinksEnabled());
+  return true;
+}
+
+bool InstantService::AddCustomLink(const GURL& url, const std::string& title) {
+  return most_visited_sites_ &&
+         most_visited_sites_->AddCustomLink(url, base::UTF8ToUTF16(title));
 }
 
 bool InstantService::UpdateCustomLink(const GURL& url,
                                       const GURL& new_url,
                                       const std::string& new_title) {
-  if (most_visited_sites_) {
-    return most_visited_sites_->UpdateCustomLink(url, new_url,
-                                                 base::UTF8ToUTF16(new_title));
-  }
-  return false;
+  return most_visited_sites_ && most_visited_sites_->UpdateCustomLink(
+                                    url, new_url, base::UTF8ToUTF16(new_title));
 }
 
 bool InstantService::ReorderCustomLink(const GURL& url, int new_pos) {
-  if (most_visited_sites_)
-    return most_visited_sites_->ReorderCustomLink(url, new_pos);
-  return false;
+  return most_visited_sites_ &&
+         most_visited_sites_->ReorderCustomLink(url, new_pos);
 }
 
 bool InstantService::DeleteCustomLink(const GURL& url) {
-  if (most_visited_sites_)
-    return most_visited_sites_->DeleteCustomLink(url);
-  return false;
+  return most_visited_sites_ && most_visited_sites_->DeleteCustomLink(url);
 }
 
 bool InstantService::UndoCustomLinkAction() {
-  // Non-Google search providers are not supported.
-  if (most_visited_sites_ && search_provider_observer_->is_google()) {
+  // Non-Google NTPs are not supported.
+  if (!most_visited_sites_ || !search_provider_observer_ ||
+      !search_provider_observer_->is_google()) {
+    return false;
+  }
   most_visited_sites_->UndoCustomLinkAction();
   return true;
-  }
-  return false;
 }
 
 bool InstantService::ResetCustomLinks() {
-  // Non-Google search providers are not supported.
-  if (most_visited_sites_ && search_provider_observer_->is_google()) {
+  // Non-Google NTPs are not supported.
+  if (!most_visited_sites_ || !search_provider_observer_ ||
+      !search_provider_observer_->is_google()) {
+    return false;
+  }
   most_visited_sites_->UninitializeCustomLinks();
   return true;
-  }
-  return false;
 }
 
 void InstantService::UpdateThemeInfo() {
@@ -472,9 +478,9 @@ void InstantService::OnRendererProcessTerminated(int process_id) {
   }
 }
 
-void InstantService::OnSearchProviderChanged(bool is_google) {
+void InstantService::OnSearchProviderChanged() {
   DCHECK(most_visited_sites_);
-  most_visited_sites_->EnableCustomLinks(is_google);
+  most_visited_sites_->EnableCustomLinks(IsCustomLinksEnabled());
 }
 
 void InstantService::OnDarkModeChanged(bool dark_mode) {
@@ -519,6 +525,11 @@ void InstantService::NotifyAboutThemeInfo() {
     observer.ThemeInfoChanged(*theme_info_);
 }
 
+bool InstantService::IsCustomLinksEnabled() {
+  return search_provider_observer_ && search_provider_observer_->is_google() &&
+         !pref_service_->GetBoolean(prefs::kNtpUseMostVisitedTiles);
+}
+
 namespace {
 
 const int kSectionBorderAlphaTransparency = 80;
@@ -777,4 +788,5 @@ void InstantService::RegisterProfilePrefs(PrefRegistrySimple* registry) {
       user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
   registry->RegisterBooleanPref(prefs::kNtpCustomBackgroundLocalToDevice,
                                 false);
+  registry->RegisterBooleanPref(prefs::kNtpUseMostVisitedTiles, false);
 }

chrome/browser/search/instant_service.h

@@ -85,6 +85,10 @@ class InstantService : public KeyedService,
   void UndoMostVisitedDeletion(const GURL& url);
   // Invoked when the Instant page wants to undo all Most Visited deletions.
   void UndoAllMostVisitedDeletions();
+  // Invoked when the Instant page wants to switch between custom links and Most
+  // Visited. Toggles between the two options each time it's called. Returns
+  // false and does nothing if the profile is using a third-party NTP.
+  bool ToggleMostVisitedOrCustomLinks();
   // Invoked when the Instant page wants to add a custom link.
   bool AddCustomLink(const GURL& url, const std::string& title);
   // Invoked when the Instant page wants to update a custom link.
@@ -96,12 +100,12 @@ class InstantService : public KeyedService,
   // Invoked when the Instant page wants to delete a custom link.
   bool DeleteCustomLink(const GURL& url);
   // Invoked when the Instant page wants to undo the previous custom link
-  // action. Returns false and does nothing if the profile is using a non-Google
-  // search provider.
+  // action. Returns false and does nothing if the profile is using a third-
+  // party NTP.
   bool UndoCustomLinkAction();
   // Invoked when the Instant page wants to delete all custom links and use Most
   // Visited sites instead. Returns false and does nothing if the profile is
-  // using a non-Google search provider. Marked virtual for mocking in tests.
+  // using a third-party NTP. Marked virtual for mocking in tests.
   virtual bool ResetCustomLinks();
 
   // Invoked to update theme information for the NTP.
@@ -156,6 +160,7 @@ class InstantService : public KeyedService,
   FRIEND_TEST_ALL_PREFIXES(InstantExtendedTest, ProcessIsolation);
   FRIEND_TEST_ALL_PREFIXES(InstantServiceTest, DeleteThumbnailDataIfExists);
   FRIEND_TEST_ALL_PREFIXES(InstantServiceTest, GetNTPTileSuggestion);
+  FRIEND_TEST_ALL_PREFIXES(InstantServiceTest, IsCustomLinksEnabled);
   FRIEND_TEST_ALL_PREFIXES(InstantServiceTest, TestNoThemeInfo);
 
   // KeyedService:
@@ -171,7 +176,7 @@ class InstantService : public KeyedService,
 
   // Called when the search provider changes. Disables custom links if the
   // search provider is not Google.
-  void OnSearchProviderChanged(bool is_google);
+  void OnSearchProviderChanged();
 
   // Called when dark mode changes. Updates current theme info as necessary and
   // notifies that the theme has changed.
@@ -186,6 +191,10 @@ class InstantService : public KeyedService,
   void NotifyAboutMostVisitedItems();
   void NotifyAboutThemeInfo();
 
+  // Returns true if this is a Google NTP and the user has chosen to show custom
+  // links.
+  bool IsCustomLinksEnabled();
+
   void BuildThemeInfo();
 
   void ApplyOrResetCustomBackgroundThemeInfo();

chrome/browser/search/instant_service_unittest.cc

@@ -106,6 +106,26 @@ TEST_F(InstantServiceTest, DeleteThumbnailDataIfExists) {
   EXPECT_FALSE(base::PathExists(database_dir));
 }
 
+TEST_F(InstantServiceTest, DoesToggleMostVisitedOrCustomLinks) {
+  sync_preferences::TestingPrefServiceSyncable* pref_service =
+      profile()->GetTestingPrefService();
+  SetUserSelectedDefaultSearchProvider("{google:baseURL}");
+  ASSERT_FALSE(pref_service->GetBoolean(prefs::kNtpUseMostVisitedTiles));
+
+  // Enable most visited tiles.
+  EXPECT_TRUE(instant_service_->ToggleMostVisitedOrCustomLinks());
+  EXPECT_TRUE(pref_service->GetBoolean(prefs::kNtpUseMostVisitedTiles));
+
+  // Disable most visited tiles.
+  EXPECT_TRUE(instant_service_->ToggleMostVisitedOrCustomLinks());
+  EXPECT_FALSE(pref_service->GetBoolean(prefs::kNtpUseMostVisitedTiles));
+
+  // Should do nothing if this is a non-Google NTP.
+  SetUserSelectedDefaultSearchProvider("https://www.search.com");
+  EXPECT_FALSE(instant_service_->ToggleMostVisitedOrCustomLinks());
+  EXPECT_FALSE(pref_service->GetBoolean(prefs::kNtpUseMostVisitedTiles));
+}
+
 TEST_F(InstantServiceTest,
        DisableUndoCustomLinkActionForNonGoogleSearchProvider) {
   SetUserSelectedDefaultSearchProvider("{google:baseURL}");
@@ -123,6 +143,25 @@ TEST_F(InstantServiceTest, DisableResetCustomLinksForNonGoogleSearchProvider) {
   EXPECT_FALSE(instant_service_->ResetCustomLinks());
 }
 
+TEST_F(InstantServiceTest, IsCustomLinksEnabled) {
+  sync_preferences::TestingPrefServiceSyncable* pref_service =
+      profile()->GetTestingPrefService();
+
+  // Test that custom links are only enabled when Most Visited is toggled off
+  // and this is a Google NTP.
+  pref_service->SetBoolean(prefs::kNtpUseMostVisitedTiles, false);
+  SetUserSelectedDefaultSearchProvider("{google:baseURL}");
+  EXPECT_TRUE(instant_service_->IsCustomLinksEnabled());
+
+  // All other cases should return false.
+  SetUserSelectedDefaultSearchProvider("https://www.search.com");
+  EXPECT_FALSE(instant_service_->IsCustomLinksEnabled());
+  pref_service->SetBoolean(prefs::kNtpUseMostVisitedTiles, true);
+  EXPECT_FALSE(instant_service_->IsCustomLinksEnabled());
+  SetUserSelectedDefaultSearchProvider("{google:baseURL}");
+  EXPECT_FALSE(instant_service_->IsCustomLinksEnabled());
+}
+
 TEST_F(InstantServiceTest, SetCustomBackgroundURL) {
   ASSERT_FALSE(instant_service_->IsCustomBackgroundSet());
   const GURL kUrl("https://www.foo.com");

chrome/browser/ui/search/search_ipc_router.cc

@@ -189,6 +189,16 @@ void SearchIPCRouter::UndoAllMostVisitedDeletions(int page_seq_no) {
   delegate_->OnUndoAllMostVisitedDeletions();
 }
 
+void SearchIPCRouter::ToggleMostVisitedOrCustomLinks(int page_seq_no) {
+  if (page_seq_no != commit_counter_)
+    return;
+
+  if (!policy_->ShouldProcessToggleMostVisitedOrCustomLinks())
+    return;
+
+  delegate_->OnToggleMostVisitedOrCustomLinks();
+}
+
 void SearchIPCRouter::AddCustomLink(int page_seq_no,
                                     const GURL& url,
                                     const std::string& title,

chrome/browser/ui/search/search_ipc_router.h

@@ -54,6 +54,10 @@ class SearchIPCRouter : public content::WebContentsObserver,
     // Called when the EmbeddedSearch wants to undo all Most Visited deletions.
     virtual void OnUndoAllMostVisitedDeletions() = 0;
 
+    // Called when the EmbeddedSearch wants to switch between custom links and
+    // Most Visited.
+    virtual void OnToggleMostVisitedOrCustomLinks() = 0;
+
     // Called when the EmbeddedSearch wants to add a custom link.
     virtual bool OnAddCustomLink(const GURL& url, const std::string& title) = 0;
 
@@ -152,6 +156,7 @@ class SearchIPCRouter : public content::WebContentsObserver,
     virtual bool ShouldProcessDeleteMostVisitedItem() = 0;
     virtual bool ShouldProcessUndoMostVisitedDeletion() = 0;
     virtual bool ShouldProcessUndoAllMostVisitedDeletions() = 0;
+    virtual bool ShouldProcessToggleMostVisitedOrCustomLinks() = 0;
     virtual bool ShouldProcessAddCustomLink() = 0;
     virtual bool ShouldProcessUpdateCustomLink() = 0;
     virtual bool ShouldProcessReorderCustomLink() = 0;
@@ -221,6 +226,7 @@ class SearchIPCRouter : public content::WebContentsObserver,
   void DeleteMostVisitedItem(int page_seq_no, const GURL& url) override;
   void UndoMostVisitedDeletion(int page_seq_no, const GURL& url) override;
   void UndoAllMostVisitedDeletions(int page_seq_no) override;
+  void ToggleMostVisitedOrCustomLinks(int page_seq_no) override;
   void AddCustomLink(int page_seq_no,
                      const GURL& url,
                      const std::string& title,

chrome/browser/ui/search/search_ipc_router_policy_impl.cc

@@ -37,6 +37,10 @@ bool SearchIPCRouterPolicyImpl::ShouldProcessUndoAllMostVisitedDeletions() {
   return !is_incognito_ && search::IsInstantNTP(web_contents_);
 }
 
+bool SearchIPCRouterPolicyImpl::ShouldProcessToggleMostVisitedOrCustomLinks() {
+  return !is_incognito_ && search::IsInstantNTP(web_contents_);
+}
+
 bool SearchIPCRouterPolicyImpl::ShouldProcessAddCustomLink() {
   return !is_incognito_ && search::IsInstantNTP(web_contents_);
 }

chrome/browser/ui/search/search_ipc_router_policy_impl.h

@@ -31,6 +31,7 @@ class SearchIPCRouterPolicyImpl : public SearchIPCRouter::Policy {
   bool ShouldProcessDeleteMostVisitedItem() override;
   bool ShouldProcessUndoMostVisitedDeletion() override;
   bool ShouldProcessUndoAllMostVisitedDeletions() override;
+  bool ShouldProcessToggleMostVisitedOrCustomLinks() override;
   bool ShouldProcessAddCustomLink() override;
   bool ShouldProcessUpdateCustomLink() override;
   bool ShouldProcessReorderCustomLink() override;

chrome/browser/ui/search/search_ipc_router_unittest.cc

@@ -61,6 +61,7 @@ class MockSearchIPCRouterDelegate : public SearchIPCRouter::Delegate {
   MOCK_METHOD1(OnDeleteMostVisitedItem, void(const GURL& url));
   MOCK_METHOD1(OnUndoMostVisitedDeletion, void(const GURL& url));
   MOCK_METHOD0(OnUndoAllMostVisitedDeletions, void());
+  MOCK_METHOD0(OnToggleMostVisitedOrCustomLinks, void());
   MOCK_METHOD2(OnAddCustomLink,
                bool(const GURL& url, const std::string& title));
   MOCK_METHOD3(OnUpdateCustomLink,
@@ -104,6 +105,7 @@ class MockSearchIPCRouterPolicy : public SearchIPCRouter::Policy {
   MOCK_METHOD0(ShouldProcessDeleteMostVisitedItem, bool());
   MOCK_METHOD0(ShouldProcessUndoMostVisitedDeletion, bool());
   MOCK_METHOD0(ShouldProcessUndoAllMostVisitedDeletions, bool());
+  MOCK_METHOD0(ShouldProcessToggleMostVisitedOrCustomLinks, bool());
   MOCK_METHOD0(ShouldProcessAddCustomLink, bool());
   MOCK_METHOD0(ShouldProcessUpdateCustomLink, bool());
   MOCK_METHOD0(ShouldProcessReorderCustomLink, bool());
@@ -488,6 +490,32 @@ TEST_F(SearchIPCRouterTest, IgnoreUndoAllMostVisitedDeletionsMsg) {
   GetSearchIPCRouter().UndoAllMostVisitedDeletions(GetSearchIPCRouterSeqNo());
 }
 
+TEST_F(SearchIPCRouterTest, ProcessToggleMostVisitedOrCustomLinksMsg) {
+  NavigateAndCommitActiveTab(GURL("chrome-search://foo/bar"));
+  SetupMockDelegateAndPolicy();
+  MockSearchIPCRouterPolicy* policy = GetSearchIPCRouterPolicy();
+  EXPECT_CALL(*mock_delegate(), OnToggleMostVisitedOrCustomLinks()).Times(1);
+  EXPECT_CALL(*policy, ShouldProcessToggleMostVisitedOrCustomLinks())
+      .Times(1)
+      .WillOnce(Return(true));
+
+  GetSearchIPCRouter().ToggleMostVisitedOrCustomLinks(
+      GetSearchIPCRouterSeqNo());
+}
+
+TEST_F(SearchIPCRouterTest, IgnoreToggleMostVisitedOrCustomLinksMsg) {
+  NavigateAndCommitActiveTab(GURL("chrome-search://foo/bar"));
+  SetupMockDelegateAndPolicy();
+  MockSearchIPCRouterPolicy* policy = GetSearchIPCRouterPolicy();
+  EXPECT_CALL(*mock_delegate(), OnToggleMostVisitedOrCustomLinks()).Times(0);
+  EXPECT_CALL(*policy, ShouldProcessToggleMostVisitedOrCustomLinks())
+      .Times(1)
+      .WillOnce(Return(false));
+
+  GetSearchIPCRouter().ToggleMostVisitedOrCustomLinks(
+      GetSearchIPCRouterSeqNo());
+}
+
 TEST_F(SearchIPCRouterTest, ProcessAddCustomLinkMsg) {
   NavigateAndCommitActiveTab(GURL("chrome-search://foo/bar"));
   SetupMockDelegateAndPolicy();

chrome/browser/ui/search/search_tab_helper.cc

@@ -293,6 +293,11 @@ void SearchTabHelper::OnUndoAllMostVisitedDeletions() {
     instant_service_->UndoAllMostVisitedDeletions();
 }
 
+void SearchTabHelper::OnToggleMostVisitedOrCustomLinks() {
+  if (instant_service_)
+    instant_service_->ToggleMostVisitedOrCustomLinks();
+}
+
 bool SearchTabHelper::OnAddCustomLink(const GURL& url,
                                       const std::string& title) {
   DCHECK(!url.is_empty());

chrome/browser/ui/search/search_tab_helper.h

@@ -101,6 +101,7 @@ class SearchTabHelper : public content::WebContentsObserver,
   void OnDeleteMostVisitedItem(const GURL& url) override;
   void OnUndoMostVisitedDeletion(const GURL& url) override;
   void OnUndoAllMostVisitedDeletions() override;
+  void OnToggleMostVisitedOrCustomLinks() override;
   bool OnAddCustomLink(const GURL& url, const std::string& title) override;
   bool OnUpdateCustomLink(const GURL& url,
                           const GURL& new_url,

chrome/common/pref_names.cc

@@ -1560,6 +1560,9 @@ const char kNtpActivateHideShortcutsFieldTrial[] =
 const char kNtpCustomBackgroundDict[] = "ntp.custom_background_dict";
 const char kNtpCustomBackgroundLocalToDevice[] =
     "ntp.custom_background_local_to_device";
+// Tracks whether the user has chosen to use custom links or most visited sites
+// for the shortcut tiles on the NTP.
+const char kNtpUseMostVisitedTiles[] = "ntp.use_most_visited_tiles";
 
 // Data associated with search suggestions that appear on the NTP.
 const char kNtpSearchSuggestionsBlocklist[] =

chrome/common/pref_names.h

@@ -538,6 +538,7 @@ extern const char kContentSuggestionsNotificationsSentCount[];
 extern const char kNtpActivateHideShortcutsFieldTrial[];
 extern const char kNtpCustomBackgroundDict[];
 extern const char kNtpCustomBackgroundLocalToDevice[];
+extern const char kNtpUseMostVisitedTiles[];
 extern const char kNtpSearchSuggestionsBlocklist[];
 extern const char kNtpSearchSuggestionsImpressions[];
 extern const char kNtpSearchSuggestionsOptOut[];

chrome/common/search.mojom

@@ -45,6 +45,9 @@ interface EmbeddedSearch {
   // Tells InstantExtended to undo one most visited item deletion.
   UndoMostVisitedDeletion(int32 page_seq_no, url.mojom.Url url);
 
+  // Tells InstantExtended to toggle between most visited items or custom links.
+  ToggleMostVisitedOrCustomLinks(int32 page_seq_no);
+
   // Tells InstantExtended to add a custom link. Returns true if successful.
   AddCustomLink(int32 page_seq_no, url.mojom.Url url, string title)
       => (bool success);

chrome/renderer/searchbox/searchbox.cc

@@ -306,6 +306,10 @@ bool SearchBox::IsCustomLinks() const {
   return is_custom_links_;
 }
 
+void SearchBox::ToggleMostVisitedOrCustomLinks() {
+  embedded_search_service_->ToggleMostVisitedOrCustomLinks(page_seq_no_);
+}
+
 void SearchBox::AddCustomLink(const GURL& url, const std::string& title) {
   if (!url.is_valid()) {
     AddCustomLinkResult(false);

chrome/renderer/searchbox/searchbox.h

@@ -112,6 +112,9 @@ class SearchBox : public content::RenderFrameObserver,
   // Returns true if the most visited items are custom links.
   bool IsCustomLinks() const;
 
+  // Sends ToggleMostVisitedOrCustomLinks to the browser.
+  void ToggleMostVisitedOrCustomLinks();
+
   // Sends AddCustomLink to the browser.
   void AddCustomLink(const GURL& url, const std::string& title);
 

chrome/renderer/searchbox/searchbox_extension.cc

@@ -600,6 +600,7 @@ class NewTabPageBindings : public gin::Wrappable<NewTabPageBindings> {
   // custom links iframe, and/or the local NTP.
   static v8::Local<v8::Value> GetMostVisitedItemData(v8::Isolate* isolate,
                                                      int rid);
+  static void ToggleMostVisitedOrCustomLinks();
   static void UpdateCustomLink(int rid,
                                const std::string& url,
                                const std::string& title);
@@ -667,6 +668,8 @@ gin::ObjectTemplateBuilder NewTabPageBindings::GetObjectTemplateBuilder(
                  &NewTabPageBindings::UndoMostVisitedDeletion)
       .SetMethod("getMostVisitedItemData",
                  &NewTabPageBindings::GetMostVisitedItemData)
+      .SetMethod("toggleMostVisitedOrCustomLinks",
+                 &NewTabPageBindings::ToggleMostVisitedOrCustomLinks)
       .SetMethod("updateCustomLink", &NewTabPageBindings::UpdateCustomLink)
       .SetMethod("reorderCustomLink", &NewTabPageBindings::ReorderCustomLink)
       .SetMethod("undoCustomLinkAction",
@@ -852,6 +855,14 @@ v8::Local<v8::Value> NewTabPageBindings::GetMostVisitedItemData(
   return GenerateMostVisitedItemData(isolate, render_view_id, rid, item);
 }
 
+// static
+void NewTabPageBindings::ToggleMostVisitedOrCustomLinks() {
+  SearchBox* search_box = GetSearchBoxForCurrentContext();
+  if (!search_box)
+    return;
+  search_box->ToggleMostVisitedOrCustomLinks();
+}
+
 // static
 void NewTabPageBindings::UpdateCustomLink(int rid,
                                           const std::string& url,

components/ntp_tiles/most_visited_sites.h

@@ -171,7 +171,8 @@ class MostVisitedSites : public history::TopSitesObserver,
   // otherwise.
   bool IsCustomLinksInitialized();
   // Enables or disables custom links, but does not (un)initialize them. Called
-  // when a third-party NTP is being used.
+  // when a third-party NTP is being used, or when the user switches between
+  // custom links and Most Visited sites.
   void EnableCustomLinks(bool enable);
   // Adds a custom link. If the number of current links is maxed, returns false
   // and does nothing. Will initialize custom links if they have not been