drm_hwcomposer: Add sanity check on display in SetLayers

Ensure that the displays given to SetLayers are actually drm displays
before referencing them in the composition_map_.

Change-Id: I87819cdb8f68ed09bf71b95dff149d5043931ffb
Signed-off-by: Sean Paul <seanpaul@chromium.org>
diff --git a/drmcomposition.cpp b/drmcomposition.cpp
index dadb053..09bdba7 100644
--- a/drmcomposition.cpp
+++ b/drmcomposition.cpp
@@ -75,6 +75,11 @@
     DrmCompositionDisplayLayersMap &map = maps[display_index];
     int display = map.display;
 
+    if (!drm_->GetConnectorForDisplay(display)) {
+      ALOGE("Invalid display given to SetLayers %d", display);
+      continue;
+    }
+
     ret = composition_map_[display]->SetLayers(map.layers.data(),
                                                map.layers.size());
     if (ret)