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/include/binder/IInterface.h b/include/binder/IInterface.h
index 5f9f69c..4ce3613 100644
--- a/include/binder/IInterface.h
+++ b/include/binder/IInterface.h
@@ -28,9 +28,9 @@
 {
 public:
             IInterface();
-            sp<IBinder>         asBinder();
-            sp<const IBinder>   asBinder() const;
-            
+            static sp<IBinder>  asBinder(const IInterface*);
+            static sp<IBinder>  asBinder(const sp<IInterface>&);
+
 protected:
     virtual                     ~IInterface();
     virtual IBinder*            onAsBinder() = 0;