drm_hwcomposer: Add getter/setter for content_type

Optionally, get the content_type drm property. Add implementation to
HwcDisplay::SetContentType to set this property.

Change-Id: I910e064876d13205abc7caaac342daaff8f38599
Signed-off-by: Sasha McIntosh <sashamcintosh@google.com>
diff --git a/drm/DrmAtomicStateManager.cpp b/drm/DrmAtomicStateManager.cpp
index 537f819..32cc68e 100644
--- a/drm/DrmAtomicStateManager.cpp
+++ b/drm/DrmAtomicStateManager.cpp
@@ -139,6 +139,11 @@
       return -EINVAL;
   }
 
+  if (args.content_type && connector->GetContentTypeProperty()) {
+    if (!connector->GetContentTypeProperty().AtomicSet(*pset, *args.content_type))
+      return -EINVAL;
+  }
+
   auto unused_planes = new_frame_state.used_planes;
 
   if (args.composition) {