Bug 1369604: Add additional comments to Highlights performance changes. r=mcomella

MozReview-Commit-ID: A5uzxbKisWF

--HG--
extra : rebase_source : dd1f11bdde21094c7bcb0ba7e4b329cbd1d32152

mobile/android/base/java/org/mozilla/gecko/activitystream/homepanel/model/Highlight.java

@@ -39,7 +39,7 @@ public class Highlight implements Item {
 
     private long historyId;
 
-    private @Nullable Metadata metadata;
+    private @Nullable Metadata metadata; // lazily-loaded.
     private @Nullable final String metadataJSON;
     private @Nullable String fastImageURL;
     private int fastDescriptionLength;

mobile/android/base/java/org/mozilla/gecko/activitystream/ranking/HighlightsRanking.java

@@ -90,6 +90,9 @@ public class HighlightsRanking {
 
     /**
      * Create a list of highlights based on the candidates provided by the input cursor.
+     *
+     * THIS METHOD IS CRITICAL FOR HIGHLIGHTS PERFORMANCE AND HAS BEEN OPTIMIZED (bug 1369604):
+     * please be careful what you add to it!
      */
     public static List<Highlight> rank(Cursor cursor, int limit) {
         List<HighlightCandidate> highlights = extractFeatures(cursor);