drm_hwcomposer: implement Gralloc 4 BufferInfoMapperMetadata

Implements the BufferInfoMapperMetadata that uses the
GraphicBufferMapper to set the fields of the hwc_drm_bo_t struct.

New class function GetFds created to obtain the file descriptors from
the native_handle_t. Function is marked weak so that vendors can
override it to match their system if required.

Change-Id: I74445487dec6bda2915b21f4b63804832bfead23
Signed-off-by: Dennis Tsiang <dennis.tsiang@arm.com>
Reviewed-by: Roman Stratiienko <r.stratiienko@gmail.com>
diff --git a/drm/DrmGenericImporter.h b/drm/DrmGenericImporter.h
index efda6be..ca53762 100644
--- a/drm/DrmGenericImporter.h
+++ b/drm/DrmGenericImporter.h
@@ -65,6 +65,7 @@
  private:
   int CloseHandle(uint32_t gem_handle);
   std::map<uint32_t, int> gem_refcount_;
+  bool has_modifier_support_;
 };
 
 }  // namespace android