Java implementation of PaymentRequest mojo service

chrome/android/java/res/layout/payment_request.xml

 <?xml version="1.0" encoding="utf-8"?>
 <!--
    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.
 -->
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:orientation="vertical">
 
@@ skipping 202 matching lines @@
                 android:textColor="#0000ff"
                 android:background="#ffffff"
                 style="?android:attr/buttonBarButtonStyle" />
 
             <Button
                 android:id="@+id/payButton"
                 android:layout_gravity="bottom"
                 android:layout_height="wrap_content"
                 android:layout_weight="1"
                 android:layout_width="0dp"
+                android:enabled="false"
                 android:text="@string/payments_pay_button"
                 android:textColor="#ffffff"
                 android:background="#0000ff"
                 style="?android:attr/buttonBarButtonStyle" />
         </LinearLayout>
 
     </LinearLayout>
 
     <LinearLayout
         android:id="@+id/waitingOverlay"
@@ skipping 20 matching lines @@
 
         <TextView
             android:id="@+id/waitingMessage"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:text="@string/payments_processing_message"
             android:textColor="@color/light_active_color"
             android:textSize="20sp" />
     </LinearLayout>
 </LinearLayout>