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 U 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 U release.

Bug: 234659204
Test: Build
Change-Id: I15aba10fe12dfcd2e67330ca844491341ef6d920

src/android/support/v7/mms/MmsNetworkManager.java

@@ -324,7 +324,8 @@ class MmsNetworkManager {
 
     private void registerConnectivityChangeReceiverLocked() {
         if (!mReceiverRegistered) {
-            mContext.registerReceiver(mConnectivityChangeReceiver, mConnectivityIntentFilter);
+            mContext.registerReceiver(mConnectivityChangeReceiver, mConnectivityIntentFilter,
+                    Context.RECEIVER_EXPORTED/*UNAUDITED*/);
             mReceiverRegistered = true;
         }
     }