ozone: Allow full screen overlay optimization for BGR formats.

ui/ozone/platform/drm/gpu/hardware_display_plane_manager.cc

Index: ui/ozone/platform/drm/gpu/hardware_display_plane_manager.cc
diff --git a/ui/ozone/platform/drm/gpu/hardware_display_plane_manager.cc b/ui/ozone/platform/drm/gpu/hardware_display_plane_manager.cc
index 6bac1893128b35c01fe0dfa2b359b0e8096ead0f..3f6f864f34c19a20208f998a58ce3a418d6ce318 100644
--- a/ui/ozone/platform/drm/gpu/hardware_display_plane_manager.cc
+++ b/ui/ozone/platform/drm/gpu/hardware_display_plane_manager.cc
@@ -266,9 +266,16 @@ bool HardwareDisplayPlaneManager::AssignOverlayPlanes(
     if (primary_plane) {
       // TODO(dcastagna): Check if we can move this optimization to
       // GLRenderer::ScheduleOverlays.
-      // Note that Chromium compositor promotes buffers to overlays (ARGB
+      // Note that Chromium compositor promotes buffers to overlays (ABGR
       // ones too) only if blending is not needed.
-      if ((fourcc_format == DRM_FORMAT_XRGB8888 ||
+      // TODO(dcastagna): this should check if the format is the same as
+      // primary_plane->format minus alpha. Changing the format of the primary
+      // plane currently works on rockchip with 3.14 kernel and won't work with

[kalyank, 2016/08/18 17:23:10]

Ideally what we want is if Kernel/hardware can swap the formats, than Kernel
should report as the supported format for the primary plane. Making this
assumptions here is something we should really avoid. That way we should be able
to enable this for all Ozone platforms. 

[Daniele Castagna, 2016/08/18 22:34:34]

AFAIK there is no interface from the kernel to know if we can swap between
different formats.

The kernel currently reports that on Intel we can't use XBGR, and we're changing
that.

This hack should go away as soon as we address crbug.com/639111, and at that
point we'll have it on all ozone drm devices.

+      // newer kernels. Remove this hack as soon as we can switch the primary
+      // plane format to match overlay buffers formats.
+      if ((fourcc_format == DRM_FORMAT_XBGR8888 ||
+           fourcc_format == DRM_FORMAT_ABGR8888 ||
+           fourcc_format == DRM_FORMAT_XRGB8888 ||
            fourcc_format == DRM_FORMAT_ARGB8888) &&
           primary_display_bounds == plane.display_bounds) {
         ResetCurrentPlaneList(plane_list);