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/gui/IGraphicBufferConsumer.cpp b/libs/gui/IGraphicBufferConsumer.cpp
index f6d087d..cc581a3 100644
--- a/libs/gui/IGraphicBufferConsumer.cpp
+++ b/libs/gui/IGraphicBufferConsumer.cpp
@@ -273,7 +273,7 @@
     virtual status_t consumerConnect(const sp<IConsumerListener>& consumer, bool controlledByApp) {
         Parcel data, reply;
         data.writeInterfaceToken(IGraphicBufferConsumer::getInterfaceDescriptor());
-        data.writeStrongBinder(consumer->asBinder());
+        data.writeStrongBinder(IInterface::asBinder(consumer));
         data.writeInt32(controlledByApp);
         status_t result = remote()->transact(CONSUMER_CONNECT, data, &reply);
         if (result != NO_ERROR) {