drm_hwcomposer: Virtual display acceleration support

Some platforms like RaspberryPI-4 can benefit from Display Blender IP Core's
ability to write back the composition into RAM, offloading the GPU in cases
where the display content needs to be used (screen record, remote display,
etc.).

To enable this feature the following system property must be enabled:

    PRODUCT_VENDOR_PROPERTIES += debug.sf.enable_hwc_vds=1

The feature was requested by the Tesla Android project to improve UI
performance.

Closes: https://gitlab.freedesktop.org/drm-hwcomposer/drm-hwcomposer/-/issues/4
Change-Id: I643f94551408bf218a0b889f1a031598646242f1
Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>
diff --git a/hwc2_device/HwcDisplayConfigs.h b/hwc2_device/HwcDisplayConfigs.h
index 98067c1..33dcb81 100644
--- a/hwc2_device/HwcDisplayConfigs.h
+++ b/hwc2_device/HwcDisplayConfigs.h
@@ -39,7 +39,7 @@
 
 struct HwcDisplayConfigs {
   HWC2::Error Update(DrmConnector &conn);
-  void FillHeadless();
+  void GenFakeMode(uint16_t width, uint16_t height);
 
   std::map<uint32_t /*config_id*/, struct HwcDisplayConfig> hwc_configs;