[Payments] Animate the scrim and bottom sheet disappearing

chrome/android/java/res/layout/payment_result.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. -->
 
 <!-- Processing dialog. -->
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:id="@+id/waiting_container"
     android:maxWidth="@dimen/payments_ui_max_dialog_width"
     android:background="@drawable/menu_bg"
@@ skipping 52 matching lines @@
     </FrameLayout>
 
     <!-- Indeterminate spinny to show that things are processing. -->
     <ProgressBar
         android:id="@+id/waiting_progress"
         android:layout_width="48dp"
         android:layout_height="48dp"
         android:layout_marginTop="@dimen/payments_section_largest_spacing"
         android:layout_marginBottom="@dimen/payments_section_small_spacing" />
 
-    <!-- Image that shows when the request was succesful. -->
-    <ImageView
-        android:id="@+id/waiting_success"
-        android:layout_width="wrap_content"
-        android:layout_height="wrap_content"
-        android:src="@drawable/verify_checkmark"
-        android:visibility="gone"
-        android:contentDescription="@null" />
-
     <!-- Message describing the result of the request. -->
     <TextView
         android:id="@+id/waiting_message"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginTop="@dimen/payments_section_small_spacing"
         android:layout_marginStart="@dimen/payments_section_large_spacing"
         android:layout_marginEnd="@dimen/payments_section_large_spacing"
         android:layout_marginBottom="@dimen/payments_section_largest_spacing"
         android:text="@string/payments_processing_message"
         android:textColor="@color/descriptive_text_color"
         android:textSize="16sp" />
 
     <!-- Dismisses the dialog. -->
     <Button
         android:id="@+id/ok_button"
         android:background="?android:attr/selectableItemBackground"
         android:text="@string/ok"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_gravity="end"
         android:layout_marginEnd="@dimen/payments_section_small_spacing"
         android:layout_marginBottom="@dimen/payments_section_small_spacing"
         android:textColor="@color/light_active_color"
         android:visibility="gone" />
 </LinearLayout>