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/services/surfaceflinger/BufferLayerConsumer.cpp b/services/surfaceflinger/BufferLayerConsumer.cpp
index 976dde2..bf61236 100644
--- a/services/surfaceflinger/BufferLayerConsumer.cpp
+++ b/services/surfaceflinger/BufferLayerConsumer.cpp
@@ -340,6 +340,7 @@
     mCurrentScalingMode = item.mScalingMode;
     mCurrentTimestamp = item.mTimestamp;
     mCurrentDataSpace = item.mDataSpace;
+    mCurrentHdrMetadata = item.mHdrMetadata;
     mCurrentFence = item.mFence;
     mCurrentFenceTime = item.mFenceTime;
     mCurrentFrameNumber = item.mFrameNumber;
@@ -447,6 +448,12 @@
     return mCurrentDataSpace;
 }
 
+const HdrMetadata& BufferLayerConsumer::getCurrentHdrMetadata() const {
+    BLC_LOGV("getCurrentHdrMetadata");
+    Mutex::Autolock lock(mMutex);
+    return mCurrentHdrMetadata;
+}
+
 uint64_t BufferLayerConsumer::getFrameNumber() {
     BLC_LOGV("getFrameNumber");
     Mutex::Autolock lock(mMutex);