Add NFC payment "how it works" screens.

Bug: 21239081
Bug: 21305138
Bug: 21305420
Change-Id: Ic9ea1b7e9b842299f2fb6b26f61a927855981e67

res/layout/nfc_payment_empty.xml

@@ -30,6 +30,7 @@
             android:id="@+id/nfc_payment_empty_text"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
+            android:gravity="center"
             android:textAppearance="?android:attr/textAppearanceLarge"
             android:textColor="?android:attr/textColorSecondary"
             android:paddingTop="32dp"

res/layout/nfc_payment_how_it_works.xml

@@ -0,0 +1,74 @@
+<?xml version="1.0" encoding="utf-8"?>
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/trusted_devices_prompt_layout"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:background="#FF80CBC4" >
+
+    <RelativeLayout
+        android:layout_width="match_parent"
+        android:layout_height="match_parent" >
+
+        <LinearLayout
+            android:layout_width="match_parent"
+            android:layout_height="200dp"
+            android:background="#FFB2DFDB" >
+        </LinearLayout>
+
+        <LinearLayout
+            android:id="@+id/nfc_how_it_works_image_text"
+            android:layout_width="match_parent"
+            android:layout_height="match_parent"
+            android:paddingLeft="16dp"
+            android:paddingRight="16dp"
+            android:paddingTop="72dp"
+            android:orientation="vertical">
+
+          <ImageView
+              android:id="@+id/nfc_how_it_works_image"
+              android:layout_width="match_parent"
+              android:layout_height="188dp"
+              android:gravity="center"
+              android:src="@drawable/nfc_how_it_works" />
+
+          <TextView
+              android:id="@+id/nfc_how_it_works_title"
+              android:layout_width="match_parent"
+              android:layout_height="wrap_content"
+              android:text="@string/nfc_how_it_works_title"
+              android:paddingLeft="74dp"
+              android:paddingRight="74dp"
+              android:textColor="#FF263238"
+              android:textSize="24sp" />
+
+          <TextView
+              android:id="@+id/nfc_how_it_works_content"
+              android:layout_width="match_parent"
+              android:layout_height="wrap_content"
+              android:paddingTop="10dp"
+              android:paddingBottom="18dp"
+              android:paddingLeft="74dp"
+              android:paddingRight="74dp"
+              android:text="@string/nfc_how_it_works_content"
+              android:textColor="#FF263238"
+              android:textSize="20sp" />
+        </LinearLayout>
+        <RelativeLayout
+            android:layout_width="match_parent"
+            android:layout_height="48dp"
+            android:layout_alignParentBottom="true"
+            android:background="#FFB2DFDB" >
+          <Button
+              android:id="@+id/nfc_how_it_works_button"
+              android:background="?android:attr/selectableItemBackground"
+              android:layout_alignParentRight="true"
+              android:layout_width="wrap_content"
+              android:layout_height="48dp"
+              android:layout_marginRight="20dp"
+              android:text="@string/nfc_how_it_works_got_it"
+              android:textSize="14sp"
+              android:textColor="#263238"
+              style="?android:attr/borderlessButtonStyle" />
+        </RelativeLayout>
+    </RelativeLayout>
+</FrameLayout>

res/values/strings.xml

@@ -5563,6 +5563,12 @@
     <string name="nfc_payment_favor_default_default_unknown">Still use default</string>
     <!-- Header for a dialog asking the user which payment app to use -->
     <string name="nfc_payment_pay_with">At a Tap &amp; pay terminal, pay with:</string>
+    <!-- Header for text explaning how to pay at a payment terminal in a store -->
+    <string name="nfc_how_it_works_title">Paying at the terminal</string>
+    <!-- Content for text explaning how to pay at a payment terminal in a store -->
+    <string name="nfc_how_it_works_content">Once you\'ve set up a Tap &amp; pay app and your phone is powered on, tap your phone on any terminal with the Tap &amp; pay logo on it to make a purchase.</string>
+    <!-- Button the user can click to indicate he understood and dismiss the screen -->
+    <string name="nfc_how_it_works_got_it">Got it</string>
     <!-- NFC More... title.  [CHAR LIMIT=40] -->
     <string name="nfc_more_title">More...</string>
     <!-- Label for the dialog that is shown when the user is asked to set a