[Android WebView] Add "about" menu with information about WebView settings to WebViewShell.

android_webview/tools/WebViewShell/res/layout/activity_webview_browser.xml

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright 2015 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.
 -->
 
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:id="@+id/container"
     android:layout_width="match_parent"
@@ skipping 11 matching lines @@
             android:layout_weight="1.0"
             android:singleLine="true"
             android:inputType="textUri"
             android:imeOptions="actionGo" />
         <ImageButton
             android:layout_width="wrap_content" 
             android:layout_height="match_parent" 
             android:src="@drawable/breadcrumb_arrow_black"
             android:contentDescription="load url"
             android:onClick="loadUrlFromUrlBar" />
+        <ImageButton
+            android:layout_width="wrap_content" 
+            android:layout_height="match_parent" 
+            android:src="@drawable/item_more_black"
+            android:color="@android:color/black"
+            android:contentDescription="something"
+            android:onClick="showPopup" />
     </LinearLayout>
     <WebView
         android:id="@+id/webview"
         android:layout_width="match_parent"
         android:layout_height="match_parent" />
 </LinearLayout>