Make getSystemService(NFC_SERVICE) the NFC entry point.

This gives NFC service a handle to the application context.

Deprecate NfcAdapter.getDefaultAdapter(), it does not provide a context.
Using this method will print a warning, and will later throw an exception
if a method that requires a context is called. No 2.3 API's will fail, but
new API's that do require a context might fail.

Also add helper NfcAdapter.getDefaultAdapter(Context).

Change-Id: I9a6378de4ef4b61ad922f8d53e64e2a1a1d5d60c

api/current.xml

@@ -35673,6 +35673,17 @@
  visibility="public"
 >
 </field>
+<field name="NFC_SERVICE"
+ type="java.lang.String"
+ transient="false"
+ volatile="false"
+ value="&quot;nfc&quot;"
+ static="true"
+ final="true"
+ deprecated="not deprecated"
+ visibility="public"
+>
+</field>
 <field name="NOTIFICATION_SERVICE"
  type="java.lang.String"
  transient="false"
@@ -100183,6 +100194,19 @@
  deprecated="not deprecated"
  visibility="public"
 >
+<parameter name="context" type="android.content.Context">
+</parameter>
+</method>
+<method name="getDefaultAdapter"
+ return="android.nfc.NfcAdapter"
+ abstract="false"
+ native="false"
+ synchronized="false"
+ static="true"
+ final="false"
+ deprecated="deprecated"
+ visibility="public"
+>
 </method>
 <method name="isEnabled"
  return="boolean"
@@ -100229,6 +100253,26 @@
 >
 </field>
 </class>
+<class name="NfcManager"
+ extends="java.lang.Object"
+ abstract="false"
+ static="false"
+ final="true"
+ deprecated="not deprecated"
+ visibility="public"
+>
+<method name="getDefaultAdapter"
+ return="android.nfc.NfcAdapter"
+ abstract="false"
+ native="false"
+ synchronized="false"
+ static="false"
+ final="false"
+ deprecated="not deprecated"
+ visibility="public"
+>
+</method>
+</class>
 </package>
 <package name="android.opengl"
 >