Replace IInterface::asBinder() with a static

so we can do NULL checks again, and update calls to IInterface::asBinder()
to use the new static version.

Change-Id: Ia7b10eb38ca55b72278bfd33d3bf647f338b4e6a
diff --git a/libs/binder/IAppOpsService.cpp b/libs/binder/IAppOpsService.cpp
index f58a352..86abdc0 100644
--- a/libs/binder/IAppOpsService.cpp
+++ b/libs/binder/IAppOpsService.cpp
@@ -91,14 +91,14 @@
         data.writeInterfaceToken(IAppOpsService::getInterfaceDescriptor());
         data.writeInt32(op);
         data.writeString16(packageName);
-        data.writeStrongBinder(callback->asBinder());
+        data.writeStrongBinder(IInterface::asBinder(callback));
         remote()->transact(START_WATCHING_MODE_TRANSACTION, data, &reply);
     }
 
     virtual void stopWatchingMode(const sp<IAppOpsCallback>& callback) {
         Parcel data, reply;
         data.writeInterfaceToken(IAppOpsService::getInterfaceDescriptor());
-        data.writeStrongBinder(callback->asBinder());
+        data.writeStrongBinder(IInterface::asBinder(callback));
         remote()->transact(STOP_WATCHING_MODE_TRANSACTION, data, &reply);
     }