Fix expected PlacementList sort order.

ui/display/display_layout.cc

Index: ui/display/display_layout.cc
diff --git a/ui/display/display_layout.cc b/ui/display/display_layout.cc
index 70784947b1c328a8203299dcc1557476a9d8820e..89b97194c26e76a840bf0db50457b5b0fb5dbdfc 100644
--- a/ui/display/display_layout.cc
+++ b/ui/display/display_layout.cc
@@ -39,7 +39,7 @@ bool IsIdInList(int64_t id, const DisplayIdList& list) {
 }
 
 bool ComparePlacements(const DisplayPlacement& d1, const DisplayPlacement& d2) {
-  return d1.display_id < d2.display_id;
+  return CompareDisplayIds(d1.display_id, d2.display_id);
 }
 
 // Extracts the displays IDs list from the displays list.
@@ -535,14 +535,16 @@ bool DisplayLayout::Validate(const DisplayIdList& list,
     return true;
 
   bool has_primary_as_parent = false;
-  int64_t prev_id = std::numeric_limits<int64_t>::min();
+  // The placement list must be sorted by the first 8 bits of the display IDs.
+  int64_t prev_id = std::numeric_limits<int8_t>::min();
   for (const auto& placement : layout.placement_list) {
     // Placements are sorted by display_id.
-    if (prev_id >= placement.display_id) {
-      LOG(ERROR) << "PlacementList must be sorted by display_id";
+    if (prev_id >= (placement.display_id & 0xFF)) {
+      LOG(ERROR) << "PlacementList must be sorted by first 8 bits of"
+                 << " display_id ";
       return false;
     }
-    prev_id = placement.display_id;
+    prev_id = (placement.display_id & 0xFF);
     if (placement.display_id == kInvalidDisplayId) {
       LOG(ERROR) << "display_id is not initialized";
       return false;