Add unaudited exported flag to exposed runtime receivers

Android T allows apps to declare a runtime receiver as not exported
by invoking registerReceiver with a new RECEIVER_NOT_EXPORTED flag;
receivers registered with this flag will only receive broadcasts from
the platform and the app itself. However to ensure developers can
properly protect their receivers, all apps targeting T or later
registering a receiver for non-system broadcasts must specify either
the exported or not exported flag when invoking #registerReceiver;
if one of these flags is not provided, the platform will throw a
SecurityException. This commit updates all the exposed receivers
with a new RECEIVER_EXPORTED_UNAUDITED flag to maintain the existing
behavior of exporting the receiver while also flagging the receiver
for audit before the T release.

Bug: 161145287
Test: Build
Change-Id: Ie97372efebd8258d9a4c503771d55109a85e6ae9

src/com/android/settings/wifi/WifiEnabler.java

@@ -118,7 +118,8 @@ public class WifiEnabler implements SwitchWidgetController.OnSwitchChangeListene
     public void resume(Context context) {
         mContext = context;
         // Wi-Fi state is sticky, so just let the receiver update UI
-        mContext.registerReceiver(mReceiver, mIntentFilter);
+        mContext.registerReceiver(mReceiver, mIntentFilter,
+                Context.RECEIVER_EXPORTED_UNAUDITED);
         if (!mListeningToOnSwitchChange) {
             mSwitchWidget.startListening();
             mListeningToOnSwitchChange = true;