ExtViews: Add action and meta-data

Services that extend KeyguardExternalViewProviderService should also
include this newly defined action in an intent-filter within the
<service> tag in their AndroidManifest.xml.  These services can also
include meta-data that defines a configuration xml which will be used
to define a settings activity that can be launched within a yet to
be defined settings/configuration UI.

Change-Id: I0a5ca09cf6f63413d067f89a9757137102dd09f6
TICKET: CYNGNOS-1687

src/java/cyanogenmod/externalviews/KeyguardExternalViewProviderService.java

@@ -57,6 +57,26 @@ public abstract class KeyguardExternalViewProviderService extends Service {
     private static final String TAG = KeyguardExternalViewProviderService.class.getSimpleName();
     private static final boolean DEBUG = false;
 
+    /**
+     * The action that must be declared as handled by this service.
+     *
+     * <p>{@code
+     *  <intent-filter>
+     *      <action android:name="cyanogenmod.externalviews.KeyguardExternalViewProviderService"/>
+     *  </intent-filter>
+     *}</p>
+     */
+    public static final String SERVICE_INTERFACE =
+            "cyanogenmod.externalviews.KeyguardExternalViewProviderService";
+
+    /**
+     * Name under which an external keyguard view publishes information about itself.
+     * This meta-data must reference an XML resource containing
+     * a <code>&lt;lockscreen&gt;</code>
+     * tag.
+     */
+    public static final String META_DATA = "cyanogenmod.externalviews.keyguard";
+
     private WindowManager mWindowManager;
     private final Handler mHandler = new Handler();