Move ApplicationThread to aidl.

Bug: 30977067
Test: Existing tests are passing, dump commands still working.
Change-Id: Iecb382e8720dfb1b6b707272497e3793e6995edb
diff --git a/services/core/java/com/android/server/am/ActivityStackSupervisor.java b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
index cd7481c..63a4e86 100644
--- a/services/core/java/com/android/server/am/ActivityStackSupervisor.java
+++ b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
@@ -3324,8 +3324,7 @@
                 try {
                     TransferPipe tp = new TransferPipe();
                     try {
-                        r.app.thread.dumpActivity(tp.getWriteFd().getFileDescriptor(),
-                                r.appToken, innerPrefix, args);
+                        r.app.thread.dumpActivity(tp.getWriteFd(), r.appToken, innerPrefix, args);
                         // Short timeout, since blocking here can
                         // deadlock with the application.
                         tp.go(fd, 2000);