Add an experimental standalone content suggestions UI.

The UI is hidden behind a feature flag that enables a menu item (which
uses innovative string compression techniques to avoid bloat due to
i18n) to open the standalone content suggestions UI.

While the activity and menu item are not meant to be shipped in an
enabled state, this will allow iterating on a content suggestions UI
outside of the NTP.

Review-Url: https://codereview.chromium.org/2593523005
Cr-Commit-Position: refs/heads/master@{#441980}

chrome/android/java/AndroidManifest.xml

@@ -413,6 +413,12 @@ by a child template that "extends" this file.
             android:hardwareAccelerated="false">
         </activity>
 
+        <activity android:name="org.chromium.chrome.browser.suggestions.ContentSuggestionsActivity"
+            android:theme="@style/FullscreenWhiteActivityTheme"
+            android:configChanges="orientation|keyboardHidden|keyboard|screenSize|mcc|mnc|screenLayout|smallestScreenSize"
+            android:windowSoftInputMode="stateAlwaysHidden">
+        </activity>
+
         <activity android:name="org.chromium.chrome.browser.sync.ui.PassphraseActivity"
             android:theme="@style/MainTheme"
             android:autoRemoveFromRecents="true">

chrome/android/java/res/menu/main_menu.xml

@@ -70,6 +70,8 @@
             android:title="@string/menu_help" />
         <item android:id="@+id/enter_vr_id"
             android:title="@string/enter_vr" />
+        <item android:id="@+id/content_suggestions_standalone_ui"
+            android:title="@string/content_suggestions_standalone_ui" />
     </group>
 
     <!-- Items shown only in the tab switcher -->

chrome/android/java/src/org/chromium/chrome/browser/ChromeFeatureList.java

@@ -68,6 +68,7 @@ public abstract class ChromeFeatureList {
     public static final String NTP_SNIPPETS_SAVE_TO_OFFLINE = "NTPSaveToOffline";
     public static final String NTP_SNIPPETS_OFFLINE_BADGE = "NTPOfflineBadge";
     public static final String NTP_SUGGESTIONS_SECTION_DISMISSAL = "NTPSuggestionsSectionDismissal";
+    public static final String NTP_SUGGESTIONS_STANDALONE_UI = "NTPSuggestionsStandaloneUI";
     public static final String SERVICE_WORKER_PAYMENT_APPS = "ServiceWorkerPaymentApps";
     public static final String TAB_REPARENTING = "TabReparenting";
     public static final String VR_SHELL = "VrShell";

chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity.java

@@ -91,6 +91,7 @@ import org.chromium.chrome.browser.preferences.PrefServiceBridge;
 import org.chromium.chrome.browser.preferences.datareduction.DataReductionPromoScreen;
 import org.chromium.chrome.browser.signin.SigninPromoUtil;
 import org.chromium.chrome.browser.snackbar.undo.UndoBarController;
+import org.chromium.chrome.browser.suggestions.ContentSuggestionsActivity;
 import org.chromium.chrome.browser.tab.BrowserControlsVisibilityDelegate;
 import org.chromium.chrome.browser.tab.Tab;
 import org.chromium.chrome.browser.tab.TabDelegateFactory;
@@ -1210,6 +1211,8 @@ public class ChromeTabbedActivity extends ChromeActivity implements OverviewMode
             RecordUserAction.record("MobileTabClosedUndoShortCut");
         } else if (id == R.id.enter_vr_id) {
             mVrShellDelegate.enterVRIfNecessary();
+        } else if (id == R.id.content_suggestions_standalone_ui) {
+            ContentSuggestionsActivity.launch(getApplicationContext());
         } else {
             return super.onMenuOrKeyboardAction(id, fromMenu);
         }

chrome/android/java/src/org/chromium/chrome/browser/appmenu/AppMenuPropertiesDelegate.java

@@ -13,6 +13,7 @@ import org.chromium.base.ApiCompatibilityUtils;
 import org.chromium.base.CommandLine;
 import org.chromium.chrome.R;
 import org.chromium.chrome.browser.ChromeActivity;
+import org.chromium.chrome.browser.ChromeFeatureList;
 import org.chromium.chrome.browser.ChromeSwitches;
 import org.chromium.chrome.browser.ShortcutHelper;
 import org.chromium.chrome.browser.UrlConstants;
@@ -188,6 +189,11 @@ public class AppMenuPropertiesDelegate {
             // Only display the Enter VR button if VR Shell Dev environment is enabled.
             menu.findItem(R.id.enter_vr_id).setVisible(
                     CommandLine.getInstance().hasSwitch(ChromeSwitches.ENABLE_VR_SHELL_DEV));
+
+            // Only display the standalone content suggestions UI if the corresponding feature
+            // is enabled.
+            menu.findItem(R.id.content_suggestions_standalone_ui).setVisible(
+                    ChromeFeatureList.isEnabled(ChromeFeatureList.NTP_SUGGESTIONS_STANDALONE_UI));
         }
 
         if (isOverviewMenu) {

chrome/android/java/src/org/chromium/chrome/browser/ntp/ContextMenuManager.java

@@ -17,7 +17,6 @@ import org.chromium.chrome.R;
 import org.chromium.chrome.browser.ntp.NewTabPageView.NewTabPageManager;
 import org.chromium.chrome.browser.ntp.snippets.SnippetsConfig;
 import org.chromium.chrome.browser.offlinepages.OfflinePageBridge;
-import org.chromium.chrome.browser.tab.Tab;
 import org.chromium.ui.base.WindowAndroid.OnCloseContextMenuListener;
 import org.chromium.ui.mojom.WindowOpenDisposition;
 
@@ -43,9 +42,10 @@ public class ContextMenuManager implements OnCloseContextMenuListener {
     public static final int ID_SAVE_FOR_OFFLINE = 3;
     public static final int ID_REMOVE = 4;
 
+    private final Activity mActivity;
     private final NewTabPageManager mManager;
-    private final Tab mTab;
     private final TouchDisableableView mOuterView;
+    private boolean mContextMenuOpen;
 
     /** Defines callback to configure the context menu and respond to user interaction. */
     public interface Delegate {
@@ -65,10 +65,10 @@ public class ContextMenuManager implements OnCloseContextMenuListener {
     /** Interface for a view that can be set to stop responding to touches. */
     public interface TouchDisableableView { void setTouchEnabled(boolean enabled); }
 
-    public ContextMenuManager(
-            NewTabPageManager newTabPageManager, Tab tab, TouchDisableableView outerView) {
+    public ContextMenuManager(Activity activity, NewTabPageManager newTabPageManager,
+            TouchDisableableView outerView) {
+        mActivity = activity;
         mManager = newTabPageManager;
-        mTab = tab;
         mOuterView = outerView;
     }
 
@@ -111,22 +111,19 @@ public class ContextMenuManager implements OnCloseContextMenuListener {
         // or swiping to dismiss an item (eg. https://crbug.com/638854, https://crbug.com/638555,
         // https://crbug.com/636296)
         mOuterView.setTouchEnabled(false);
-
-        mTab.getWindowAndroid().addContextMenuCloseListener(this);
+        mContextMenuOpen = true;
     }
 
     @Override
     public void onContextMenuClosed() {
+        if (!mContextMenuOpen) return;
         mOuterView.setTouchEnabled(true);
-        mTab.getWindowAndroid().removeContextMenuCloseListener(this);
+        mContextMenuOpen = false;
     }
 
     /** Closes the context menu, if open. */
     public void closeContextMenu() {
-        Activity activity = mTab.getWindowAndroid().getActivity().get();
-        if (activity == null) return;
-
-        activity.closeContextMenu();
+        mActivity.closeContextMenu();
     }
 
     private boolean shouldShowItem(@ContextMenuItemId int itemId, Delegate delegate) {

chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPageView.java

@@ -361,8 +361,15 @@ public class NewTabPageView extends FrameLayout
             mScrollView.enableBottomShadow(SHADOW_COLOR);
             mNewTabPageLayout = (NewTabPageLayout) findViewById(R.id.ntp_content);
         }
-        mContextMenuManager =
-                new ContextMenuManager(mManager, tab, mUseCardsUi ? mRecyclerView : mScrollView);
+        mContextMenuManager = new ContextMenuManager(mActivity, mManager,
+                mUseCardsUi ? mRecyclerView : mScrollView);
+        mActivity.getWindowAndroid().addContextMenuCloseListener(mContextMenuManager);
+        manager.addDestructionObserver(new DestructionObserver() {
+            @Override
+            public void onDestroy() {
+                mActivity.getWindowAndroid().removeContextMenuCloseListener(mContextMenuManager);
+            }
+        });
 
         mMostVisitedDesign = new MostVisitedDesign(getContext());
         mMostVisitedLayout =

chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java

@@ -4,6 +4,7 @@
 
 package org.chromium.chrome.browser.ntp.cards;
 
+import android.support.annotation.Nullable;
 import android.support.v7.widget.RecyclerView;
 import android.support.v7.widget.RecyclerView.Adapter;
 import android.support.v7.widget.RecyclerView.ViewHolder;
@@ -27,32 +28,34 @@ import org.chromium.chrome.browser.offlinepages.OfflinePageBridge;
  */
 public class NewTabPageAdapter extends Adapter<NewTabPageViewHolder> implements NodeParent {
     private final NewTabPageManager mNewTabPageManager;
+    @Nullable
     private final View mAboveTheFoldView;
     private final UiConfig mUiConfig;
     private NewTabPageRecyclerView mRecyclerView;
 
     private final InnerNode mRoot;
 
-    private final AboveTheFoldItem mAboveTheFold = new AboveTheFoldItem();
+    @Nullable
+    private final AboveTheFoldItem mAboveTheFold;
     private final SectionList mSections;
     private final SignInPromo mSigninPromo;
     private final AllDismissedItem mAllDismissed;
     private final Footer mFooter;
-    private final SpacingItem mBottomSpacer = new SpacingItem();
+    private final SpacingItem mBottomSpacer;
 
     /**
      * Creates the adapter that will manage all the cards to display on the NTP.
      *
      * @param manager the NewTabPageManager to use to interact with the rest of the system.
      * @param aboveTheFoldView the layout encapsulating all the above-the-fold elements
-     *                         (logo, search box, most visited tiles)
+     *         (logo, search box, most visited tiles), or null if only suggestions should
+     *         be displayed.
      * @param uiConfig the NTP UI configuration, to be passed to created views.
      * @param offlinePageBridge the OfflinePageBridge used to determine if articles are available
-     *                              offline.
-     *
+     *         offline.
      */
-    public NewTabPageAdapter(NewTabPageManager manager, View aboveTheFoldView, UiConfig uiConfig,
-            OfflinePageBridge offlinePageBridge) {
+    public NewTabPageAdapter(NewTabPageManager manager, @Nullable View aboveTheFoldView,
+            UiConfig uiConfig, OfflinePageBridge offlinePageBridge) {
         mNewTabPageManager = manager;
         mAboveTheFoldView = aboveTheFoldView;
         mUiConfig = uiConfig;
@@ -63,8 +66,19 @@ public class NewTabPageAdapter extends Adapter<NewTabPageViewHolder> implements
         mAllDismissed = new AllDismissedItem();
         mFooter = new Footer();
 
-        mRoot.addChildren(
-                mAboveTheFold, mSections, mSigninPromo, mAllDismissed, mFooter, mBottomSpacer);
+        if (mAboveTheFoldView == null) {
+            mAboveTheFold = null;
+        } else {
+            mAboveTheFold = new AboveTheFoldItem();
+            mRoot.addChild(mAboveTheFold);
+        }
+        mRoot.addChildren(mSections, mSigninPromo, mAllDismissed, mFooter);
+        if (mAboveTheFoldView == null) {
+            mBottomSpacer = null;
+        } else {
+            mBottomSpacer = new SpacingItem();
+            mRoot.addChild(mBottomSpacer);
+        }
 
         updateAllDismissedVisibility();
         mRoot.setParent(this);
@@ -127,6 +141,8 @@ public class NewTabPageAdapter extends Adapter<NewTabPageViewHolder> implements
     }
 
     public int getAboveTheFoldPosition() {
+        if (mAboveTheFoldView == null) return RecyclerView.NO_POSITION;
+
         return getChildPositionOffset(mAboveTheFold);
     }
 
@@ -146,6 +162,8 @@ public class NewTabPageAdapter extends Adapter<NewTabPageViewHolder> implements
     }
 
     int getBottomSpacerPosition() {
+        if (mBottomSpacer == null) return RecyclerView.NO_POSITION;
+
         return getChildPositionOffset(mBottomSpacer);
     }
 
@@ -165,7 +183,7 @@ public class NewTabPageAdapter extends Adapter<NewTabPageViewHolder> implements
     public void onItemRangeInserted(TreeNode child, int itemPosition, int itemCount) {
         assert child == mRoot;
         notifyItemRangeInserted(itemPosition, itemCount);
-        mBottomSpacer.refresh();
+        if (mBottomSpacer != null) mBottomSpacer.refresh();
 
         updateAllDismissedVisibility();
     }
@@ -174,7 +192,7 @@ public class NewTabPageAdapter extends Adapter<NewTabPageViewHolder> implements
     public void onItemRangeRemoved(TreeNode child, int itemPosition, int itemCount) {
         assert child == mRoot;
         notifyItemRangeRemoved(itemPosition, itemCount);
-        mBottomSpacer.refresh();
+        if (mBottomSpacer != null) mBottomSpacer.refresh();
 
         updateAllDismissedVisibility();
     }

chrome/android/java/src/org/chromium/chrome/browser/suggestions/ContentSuggestionsActivity.java

+// Copyright 2016 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.
+
+package org.chromium.chrome.browser.suggestions;
+
+import android.content.Context;
+import android.content.Intent;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.Menu;
+
+import org.chromium.base.Callback;
+import org.chromium.base.ObserverList;
+import org.chromium.chrome.R;
+import org.chromium.chrome.browser.ChromeFeatureList;
+import org.chromium.chrome.browser.SynchronousInitializationActivity;
+import org.chromium.chrome.browser.favicon.FaviconHelper.FaviconImageCallback;
+import org.chromium.chrome.browser.favicon.FaviconHelper.IconAvailabilityCallback;
+import org.chromium.chrome.browser.favicon.LargeIconBridge.LargeIconCallback;
+import org.chromium.chrome.browser.ntp.ContextMenuManager;
+import org.chromium.chrome.browser.ntp.LogoBridge.LogoObserver;
+import org.chromium.chrome.browser.ntp.MostVisitedItem;
+import org.chromium.chrome.browser.ntp.NewTabPage.DestructionObserver;
+import org.chromium.chrome.browser.ntp.NewTabPageView.NewTabPageManager;
+import org.chromium.chrome.browser.ntp.UiConfig;
+import org.chromium.chrome.browser.ntp.cards.NewTabPageAdapter;
+import org.chromium.chrome.browser.ntp.cards.NewTabPageRecyclerView;
+import org.chromium.chrome.browser.ntp.snippets.SnippetArticle;
+import org.chromium.chrome.browser.ntp.snippets.SnippetsBridge;
+import org.chromium.chrome.browser.ntp.snippets.SuggestionsSource;
+import org.chromium.chrome.browser.offlinepages.OfflinePageBridge;
+import org.chromium.chrome.browser.profiles.MostVisitedSites.MostVisitedURLsObserver;
+import org.chromium.chrome.browser.profiles.Profile;
+
+import java.util.Set;
+
+/**
+ * Experimental activity to show content suggestions outside of the New Tab Page.
+ */
+public class ContentSuggestionsActivity extends SynchronousInitializationActivity {
+    private final ObserverList<DestructionObserver> mDestructionObservers = new ObserverList<>();
+
+    private ContextMenuManager mContextMenuManager;
+    private SnippetsBridge mSnippetsBridge;
+    private NewTabPageRecyclerView mRecyclerView;
+
+    public static void launch(Context context) {
+        Intent intent = new Intent();
+        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
+        intent.setClass(context, ContentSuggestionsActivity.class);
+        context.startActivity(intent);
+    }
+
+    private class SuggestionsNewTabPageManager implements NewTabPageManager {
+        @Override
+        public void removeMostVisitedItem(MostVisitedItem item) {}
+
+        @Override
+        public void openMostVisitedItem(int windowDisposition, MostVisitedItem item) {}
+
+        @Override
+        public boolean isLocationBarShownInNTP() {
+            return false;
+        }
+
+        @Override
+        public boolean isVoiceSearchEnabled() {
+            return false;
+        }
+
+        @Override
+        public boolean isFakeOmniboxTextEnabledTablet() {
+            return false;
+        }
+
+        @Override
+        public boolean isOpenInNewWindowEnabled() {
+            return true;
+        }
+
+        @Override
+        public boolean isOpenInIncognitoEnabled() {
+            return true;
+        }
+
+        @Override
+        public void navigateToBookmarks() {}
+
+        @Override
+        public void navigateToRecentTabs() {}
+
+        @Override
+        public void navigateToDownloadManager() {}
+
+        @Override
+        public void trackSnippetsPageImpression(int[] categories, int[] suggestionsPerCategory) {}
+
+        @Override
+        public void trackSnippetImpression(SnippetArticle article) {}
+
+        @Override
+        public void trackSnippetMenuOpened(SnippetArticle article) {}
+
+        @Override
+        public void trackSnippetCategoryActionImpression(int category, int position) {}
+
+        @Override
+        public void trackSnippetCategoryActionClick(int category, int position) {}
+
+        @Override
+        public void openSnippet(int windowOpenDisposition, SnippetArticle article) {}
+
+        @Override
+        public void focusSearchBox(boolean beginVoiceSearch, String pastedText) {}
+
+        @Override
+        public void setMostVisitedURLsObserver(MostVisitedURLsObserver observer, int numResults) {}
+
+        @Override
+        public void getLocalFaviconImageForURL(
+                String url, int size, FaviconImageCallback faviconCallback) {}
+
+        @Override
+        public void getLargeIconForUrl(String url, int size, LargeIconCallback callback) {}
+
+        @Override
+        public void ensureIconIsAvailable(String pageUrl, String iconUrl, boolean isLargeIcon,
+                boolean isTemporary, IconAvailabilityCallback callback) {}
+
+        @Override
+        public void getUrlsAvailableOffline(Set<String> pageUrls, Callback<Set<String>> callback) {}
+
+        @Override
+        public void onLogoClicked(boolean isAnimatedLogoShowing) {}
+
+        @Override
+        public void getSearchProviderLogo(LogoObserver logoObserver) {}
+
+        @Override
+        public void onLoadingComplete(MostVisitedItem[] mostVisitedItems) {}
+
+        @Override
+        public void onLearnMoreClicked() {}
+
+        @Override
+        public SuggestionsSource getSuggestionsSource() {
+            return mSnippetsBridge;
+        }
+
+        @Override
+        public void addDestructionObserver(DestructionObserver destructionObserver) {
+            mDestructionObservers.addObserver(destructionObserver);
+        }
+
+        @Override
+        public boolean isCurrentPage() {
+            return true;
+        }
+
+        @Override
+        public ContextMenuManager getContextMenuManager() {
+            return mContextMenuManager;
+        }
+    }
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        assert ChromeFeatureList.isEnabled(ChromeFeatureList.NTP_SUGGESTIONS_STANDALONE_UI);
+
+        mRecyclerView = (NewTabPageRecyclerView) LayoutInflater.from(this).inflate(
+                R.layout.new_tab_page_recycler_view, null, false);
+
+        Profile profile = Profile.getLastUsedProfile();
+        mSnippetsBridge = new SnippetsBridge(profile);
+
+        NewTabPageManager manager = new SuggestionsNewTabPageManager();
+        mContextMenuManager = new ContextMenuManager(this, manager, mRecyclerView);
+        UiConfig uiConfig = new UiConfig(mRecyclerView);
+        NewTabPageAdapter adapter = new NewTabPageAdapter(
+                manager, null, uiConfig, OfflinePageBridge.getForProfile(profile));
+        mRecyclerView.setAdapter(adapter);
+        mRecyclerView.setUpSwipeToDismiss();
+
+        setContentView(mRecyclerView);
+    }
+
+    @Override
+    public void onContextMenuClosed(Menu menu) {
+        mContextMenuManager.onContextMenuClosed();
+    }
+
+    @Override
+    protected void onDestroy() {
+        for (DestructionObserver observer : mDestructionObservers) {
+            observer.onDestroy();
+        }
+        super.onDestroy();
+    }
+}

chrome/android/java/src/org/chromium/chrome/browser/suggestions/OWNERS

+file://chrome/android/java/src/org/chromium/chrome/browser/ntp/OWNERS
\ No newline at end of file

chrome/android/java/strings/android_chrome_strings.grd

@@ -2877,6 +2877,11 @@ You can control the Physical Web in Chrome Settings.
       <message name="IDS_KEYBOARD_SHORTCUT_WEBPAGE_GROUP_HEADER" desc="A text label that appears above a list of shortcuts that are related to manipulation of the current tab window. This group is part of several groups of keyboard shortcuts all shown in a dialog.">
         Webpage shortcuts
       </message>
+
+      <!-- Content suggestion strings -->
+      <message name="IDS_CONTENT_SUGGESTIONS_STANDALONE_UI" desc="A text label for the menu item to open the content suggestions standalone UI." translateable="false">
+        🔰🆕👌
+      </message>
     </messages>
   </release>
 </grit>

chrome/android/java_sources.gni

@@ -919,6 +919,7 @@ chrome_java_sources = [
   "java/src/org/chromium/chrome/browser/snackbar/smartlockautosignin/AutoSigninSnackbarController.java",
   "java/src/org/chromium/chrome/browser/snackbar/undo/UndoBarController.java",
   "java/src/org/chromium/chrome/browser/ssl/SecurityStateModel.java",
+  "java/src/org/chromium/chrome/browser/suggestions/ContentSuggestionsActivity.java",
   "java/src/org/chromium/chrome/browser/superviseduser/SupervisedUserContentProvider.java",
   "java/src/org/chromium/chrome/browser/sync/GmsCoreSyncListener.java",
   "java/src/org/chromium/chrome/browser/sync/GoogleServiceAuthError.java",

chrome/android/javatests/src/org/chromium/chrome/browser/ntp/snippets/ArticleSnippetsTest.java

@@ -210,7 +210,8 @@ public class ArticleSnippetsTest extends ChromeActivityTestCaseBase<ChromeActivi
      */
     private class MockNewTabPageManager implements NewTabPageManager {
         // TODO(dgn): provide a RecyclerView if we need to test the context menu.
-        private ContextMenuManager mContextMenuManager = new ContextMenuManager(this, null, null);
+        private ContextMenuManager mContextMenuManager =
+                new ContextMenuManager(getActivity(), this, null);
 
         @Override
         public void getLocalFaviconImageForURL(

chrome/android/junit/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapterTest.java

@@ -29,6 +29,7 @@ import static org.chromium.chrome.browser.ntp.cards.ContentSuggestionsTestUtils.
 import android.content.res.Resources;
 import android.support.v7.widget.RecyclerView;
 import android.support.v7.widget.RecyclerView.AdapterDataObserver;
+import android.view.View;
 
 import org.junit.After;
 import org.junit.Before;
@@ -971,7 +972,8 @@ public class NewTabPageAdapterTest {
     }
 
     private void reloadNtp() {
-        mAdapter = new NewTabPageAdapter(mNewTabPageManager, null, null, mOfflinePageBridge);
+        mAdapter = new NewTabPageAdapter(mNewTabPageManager, mock(View.class), null,
+                mOfflinePageBridge);
     }
 
     private void assertArticlesEqual(List<SnippetArticle> articles, int start, int end) {

chrome/browser/android/chrome_feature_list.cc

@@ -51,6 +51,7 @@ const base::Feature* kFeaturesExposedToJava[] = {
     &kNoCreditCardAbort,
     &kNTPFakeOmniboxTextFeature,
     &kNTPOfflinePagesFeature,
+    &kNTPSuggestionsStandaloneUIFeature,
     &kPhysicalWebFeature,
     &kPhysicalWebIgnoreOtherClientsFeature,
     &kSpecialLocaleFeature,
@@ -113,6 +114,9 @@ const base::Feature kNTPFakeOmniboxTextFeature{
 const base::Feature kNTPOfflinePagesFeature{"NTPOfflinePages",
                                             base::FEATURE_ENABLED_BY_DEFAULT};
 
+const base::Feature kNTPSuggestionsStandaloneUIFeature{
+    "NTPSuggestionsStandaloneUI", base::FEATURE_DISABLED_BY_DEFAULT};
+
 const base::Feature kPhysicalWebFeature{"PhysicalWeb",
                                         base::FEATURE_ENABLED_BY_DEFAULT};
 

chrome/browser/android/chrome_feature_list.h

@@ -26,6 +26,7 @@ extern const base::Feature kNativeAndroidHistoryManager;
 extern const base::Feature kNoCreditCardAbort;
 extern const base::Feature kNTPFakeOmniboxTextFeature;
 extern const base::Feature kNTPOfflinePagesFeature;
+extern const base::Feature kNTPSuggestionsStandaloneUIFeature;
 extern const base::Feature kPhysicalWebFeature;
 extern const base::Feature kPhysicalWebIgnoreOtherClientsFeature;
 extern const base::Feature kSpecialLocaleFeature;