drm_hwcomposer: have DrmDisplayCompositor do its own OpenGL composition

To accomplish this a few things changed:
- DrmComposition::GetRemainingLayers always returns the number of planes needed
- DrmComposition::AddLayer succeeds even if no DrmPlane was found for it
- DrmDisplayComposition::AddLayer has overload that imports the given buffer
- GLWorkerCompositor has a function to finish its composite before returning

Put together this change makes DrmComposition always accepts all layers given to
it even if it means some of those layers are assigned a NULL DrmPlane. The
DrmDisplayCompositor will scan its given layers for any that are missing planes.
In such a case, a DrmPlane is stolen from the last layer to receive a plane.
Then all layers in the DrmDisplayComposition that have no planes (including the
one stolen from) are composited synchronously using a GLWorkerCompositor and a
new layer is generated from the results. That layer is added to the
DrmDisplayComposition using the new import AddLayer function and the stolen
DrmPlane. DrmDisplayCompostior then continues as usual.

Change-Id: Ia6477c210c8f1307a4e537bec46889110d79ca18

1 files changed, 3 insertions, 0 deletions

diff --git a/drmdisplaycomposition.h b/drmdisplaycomposition.h
index 1df8dee..9c51078 100644
--- a/drmdisplaycomposition.h
+++ b/drmdisplaycomposition.h
@@ -56,6 +56,9 @@ class DrmDisplayComposition {
 
   int AddLayer(hwc_layer_1_t *layer, hwc_drm_bo_t *bo, DrmCrtc *crtc,
                DrmPlane *plane);
+  // Like the AddLayer that accepts a hwc_drm_bo_t, but uses Importer to import
+  // the layer->handle itself.
+  int AddLayer(hwc_layer_1_t *layer, DrmCrtc *crtc, DrmPlane *plane);
   int AddPlaneDisable(DrmPlane *plane);
   int AddDpmsMode(uint32_t dpms_mode);