Add sideband streams to BufferQueue and related classes

Sideband streams are essentially a device-specific buffer queue that
bypasses the BufferQueue system. They can be used for situations with
hard real-time requirements like high-quality TV and video playback
with A/V sync. A handle to the stream is provided by the source HAL,
and attached to a BufferQueue. The sink HAL can read buffers via the
stream handle rather than acquiring individual buffers from the
BufferQueue.

Change-Id: Ib3f262eddfc520f4bbe3d9b91753ed7dd09d3a9b
diff --git a/libs/gui/BufferQueueConsumer.cpp b/libs/gui/BufferQueueConsumer.cpp
index dc7aa15..e34f716 100644
--- a/libs/gui/BufferQueueConsumer.cpp
+++ b/libs/gui/BufferQueueConsumer.cpp
@@ -395,6 +395,10 @@
     return NO_ERROR;
 }
 
+sp<NativeHandle> BufferQueueConsumer::getSidebandStream() const {
+    return mCore->mSidebandStream;
+}
+
 void BufferQueueConsumer::dump(String8& result, const char* prefix) const {
     mCore->dump(result, prefix);
 }