Add plumbing for HDR metadata

Allow a ANativeWindow client to send HDR metadata to SurfaceFlinger.
The metadata can be queried with
BufferLayerConsumer::getCurrentHdrMetadata.

Written by Courtney.  Updated by olv@.

Bug: 63710530
Test: builds
Change-Id: I23192d4750950664b57863a533bffd72397255b4
diff --git a/libs/gui/Android.bp b/libs/gui/Android.bp
index c713e9e..7ee4d49 100644
--- a/libs/gui/Android.bp
+++ b/libs/gui/Android.bp
@@ -92,6 +92,7 @@
         "FrameTimestamps.cpp",
         "GLConsumer.cpp",
         "GuiConfig.cpp",
+        "HdrMetadata.cpp",
         "IDisplayEventConnection.cpp",
         "IConsumerListener.cpp",
         "IGraphicBufferConsumer.cpp",