Add an experimental standalone content suggestions UI.

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

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/ContextMenuManager.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/ContextMenuManager.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/ContextMenuManager.java
index fda2dde2e44a70f861edf9433745d4a84ba75af1..36f81a5ce8a3d773d43fa0333b16521762d4541f 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/ContextMenuManager.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/ContextMenuManager.java
@@ -6,6 +6,7 @@ package org.chromium.chrome.browser.ntp;
 
 import android.app.Activity;
 import android.support.annotation.IntDef;
+import android.support.annotation.Nullable;
 import android.support.annotation.StringRes;
 import android.support.v13.view.ViewCompat;
 import android.view.ContextMenu;
@@ -45,6 +46,7 @@ public class ContextMenuManager implements OnCloseContextMenuListener {
     public static final int ID_REMOVE = 4;
 
     private final NewTabPageManager mManager;
+    @Nullable
     private final Tab mTab;
     private final TouchDisableableView mOuterView;
 
@@ -67,7 +69,8 @@ public class ContextMenuManager implements OnCloseContextMenuListener {
     public interface TouchDisableableView { void setTouchEnabled(boolean enabled); }
 
     public ContextMenuManager(
-            NewTabPageManager newTabPageManager, Tab tab, TouchDisableableView outerView) {
+            NewTabPageManager newTabPageManager, @Nullable Tab tab,
+            TouchDisableableView outerView) {
         mManager = newTabPageManager;
         mTab = tab;
         mOuterView = outerView;
@@ -111,9 +114,10 @@ public class ContextMenuManager implements OnCloseContextMenuListener {
         // prevent the user long pressing to get the context menu then on the same press scrolling
         // 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);
+        if (mTab != null) {
+            mOuterView.setTouchEnabled(false);
+            mTab.getWindowAndroid().addContextMenuCloseListener(this);

[dgn, 2017/01/04 12:19:43]

Activity#onContextMenuClosed as a substitute maybe? We could add something to
NTPManager to expose it.

[Bernhard Bauer, 2017/01/05 12:02:15]

As discussed offline, changed ContextMenuManager so it will stay registered as a
ContextMenuCloseListener.

+        }
     }
 
     @Override
@@ -124,6 +128,8 @@ public class ContextMenuManager implements OnCloseContextMenuListener {
 
     /** Closes the context menu, if open. */
     public void closeContextMenu() {

[dgn, 2017/01/04 12:19:43]

we also use this method to close the menu when changing orientation. Provide the
ContentSuggestionActivity instead of using the tab to get one?

[Bernhard Bauer, 2017/01/05 12:02:15]

Done.

+        if (mTab == null) return;
+
         Activity activity = mTab.getWindowAndroid().getActivity().get();
         if (activity == null) return;