Introduce permission for updating the cell broadcast content provider.

Change-Id: I64a1001b6aaf7c0032cde01216abb240c54520f7
diff --git a/core/res/AndroidManifest.xml b/core/res/AndroidManifest.xml
index 062ae27..c788b96 100644
--- a/core/res/AndroidManifest.xml
+++ b/core/res/AndroidManifest.xml
@@ -824,6 +824,11 @@
     <permission android:name="android.permission.BIND_DIRECTORY_SEARCH"
         android:protectionLevel="signature|privileged" />
 
+    <!-- @SystemApi @hide Allows an application to modify cell broadcasts through the content provider.
+         <p>Not for use by third-party applications. -->
+    <permission android:name="android.permission.MODIFY_CELL_BROADCASTS"
+                android:protectionLevel="signature|system" />
+
     <!-- =============================================================== -->
     <!-- Permissions for setting the device alarm                        -->
     <!-- =============================================================== -->