[Touchless] Add context menu to "More" button on NTP

BUG=959317
R=skym@chromium.org,mdjones@chromium.org

Change-Id: Icb49eaac8aed5f66fbe16d12d615bb1f8567bbaa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1636854Reviewed-by: Matthew Jones <mdjones@chromium.org>
Reviewed-by: Sky Malice <skym@chromium.org>
Commit-Queue: Pavel Yatsuk <pavely@chromium.org>
Cr-Commit-Position: refs/heads/master@{#665007}

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

@@ -84,6 +84,36 @@ public class ContextMenuManager implements OnCloseContextMenuListener {
         void onContextMenuCreated();
     }
 
+    /**
+     * Empty implementation of Delegate to allow derived classes to only implement methods they
+     * need.
+     */
+    public static class EmptyDelegate implements Delegate {
+        @Override
+        public void openItem(int windowDisposition) {}
+
+        @Override
+        public void removeItem() {}
+
+        @Override
+        public String getUrl() {
+            return null;
+        }
+
+        @Override
+        public String getContextMenuTitle() {
+            return null;
+        }
+
+        @Override
+        public boolean isItemSupported(@ContextMenuItemId int menuItemId) {
+            return false;
+        }
+
+        @Override
+        public void onContextMenuCreated() {}
+    }
+
     /**
      * Delegate used by the {@link ContextMenuManager} to disable touch events on the outer view
      * while the context menu is open.

chrome/android/touchless/java/src/org/chromium/chrome/browser/touchless/TouchlessActionItemViewHolder.java

@@ -11,6 +11,7 @@ import android.widget.TextView;
 import org.chromium.base.ApiCompatibilityUtils;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.chrome.browser.native_page.ContextMenuManager;
+import org.chromium.chrome.browser.native_page.ContextMenuManager.ContextMenuItemId;
 import org.chromium.chrome.browser.ntp.cards.ActionItem;
 import org.chromium.chrome.browser.suggestions.SuggestionsRecyclerView;
 import org.chromium.chrome.browser.suggestions.SuggestionsUiDelegate;
@@ -48,6 +49,18 @@ class TouchlessActionItemViewHolder extends ActionItem.ViewHolder {
                 ApiCompatibilityUtils.getDrawable(itemView.getResources(), R.drawable.ic_note_add));
         // Image view defaults to GONE.
         mImageView.setVisibility(View.VISIBLE);
+        ContextMenuManager.registerViewForTouchlessContextMenu(
+                mButton, new ContextMenuManager.EmptyDelegate() {
+                    @Override
+                    public String getContextMenuTitle() {
+                        return mButton.getResources().getString(R.string.more_articles);
+                    }
+
+                    @Override
+                    public boolean isItemSupported(@ContextMenuItemId int menuItemId) {
+                        return menuItemId == ContextMenuItemId.LEARN_MORE;
+                    }
+                });
     }
 
     @Override