stagefright: fix pushBlankBuffersToNW for non-meta decoders

Bug: 20709429
Change-Id: Ifaee74083dedecb755e5c8ba3369cf90dfd74035
diff --git a/media/libstagefright/ACodec.cpp b/media/libstagefright/ACodec.cpp
index b7798d2..22395cc 100644
--- a/media/libstagefright/ACodec.cpp
+++ b/media/libstagefright/ACodec.cpp
@@ -4156,6 +4156,9 @@
         goto error;
     }
 
+    static_cast<Surface*>(mNativeWindow.get())
+            ->getIGraphicBufferProducer()->allowAllocation(true);
+
     err = mNativeWindow->query(mNativeWindow.get(),
             NATIVE_WINDOW_MIN_UNDEQUEUED_BUFFERS, &minUndequeuedBufs);
     if (err != NO_ERROR) {