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/StreamSplitter.cpp b/libs/gui/StreamSplitter.cpp
index 5f39905..25e6cab 100644
--- a/libs/gui/StreamSplitter.cpp
+++ b/libs/gui/StreamSplitter.cpp
@@ -80,7 +80,7 @@
 
     IGraphicBufferProducer::QueueBufferOutput queueBufferOutput;
     sp<OutputListener> listener(new OutputListener(this, outputQueue));
-    outputQueue->asBinder()->linkToDeath(listener);
+    IInterface::asBinder(outputQueue)->linkToDeath(listener);
     status_t status = outputQueue->connect(listener, NATIVE_WINDOW_API_CPU,
             /* producerControlledByApp */ false, &queueBufferOutput);
     if (status != NO_ERROR) {