drm_hwcomposer: Set correct size for changed composition types
Call HwcDisplay::GetChangedCompositionTypes with nullptrs to get the correct expected number of changed composition types.
Resizing this incorrectly resulted in entries for default-initialized layer id (0), leading to log spam and possibly impacting performance as well.
Addresses the log spam reported in #95.
Change-Id: I84046f9bc461656214f0a1f0ca0c440a7189505b Signed-off-by: Drew Davenport ddavenport@google.com