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, 2 insertions, 0 deletions

diff --git a/glworker.h b/glworker.h
index e9febec..9550cbe 100644
--- a/glworker.h
+++ b/glworker.h
@@ -88,6 +88,8 @@ class GLWorkerCompositor {
 
   int Composite(hwc_layer_1 *layers, size_t num_layers,
                 sp<GraphicBuffer> framebuffer);
+  int CompositeAndFinish(hwc_layer_1 *layers, size_t num_layers,
+                         sp<GraphicBuffer> framebuffer);
 
  private:
   EGLDisplay egl_display_;