Make header decorations play well together

// FREEBIE

src/org/thoughtcrime/securesms/ConversationAdapter.java

@@ -353,12 +353,12 @@ public class ConversationAdapter <V extends View & BindableConversationItem>
     viewHolder.setText(getContext().getResources().getQuantityString(R.plurals.ConversationAdapter_n_unread_messages, (position + 1), (position + 1)));
   }
 
-  public static class LastSeenHeader extends StickyHeaderDecoration {
+  static class LastSeenHeader extends StickyHeaderDecoration {
 
     private final ConversationAdapter adapter;
     private final long                lastSeenTimestamp;
 
-    public LastSeenHeader(ConversationAdapter adapter, long lastSeenTimestamp) {
+    LastSeenHeader(ConversationAdapter adapter, long lastSeenTimestamp) {
       super(adapter, false, false);
       this.adapter           = adapter;
       this.lastSeenTimestamp = lastSeenTimestamp;
@@ -380,6 +380,11 @@ public class ConversationAdapter <V extends View & BindableConversationItem>
       return currentRecordTimestamp > lastSeenTimestamp && previousRecordTimestamp < lastSeenTimestamp;
     }
 
+    @Override
+    protected int getHeaderTop(RecyclerView parent, View child, View header, int adapterPos, int layoutPos) {
+      return parent.getLayoutManager().getDecoratedTop(child);
+    }
+
     @Override
     protected HeaderViewHolder getHeader(RecyclerView parent, StickyHeaderAdapter stickyAdapter, int position) {
       HeaderViewHolder viewHolder = adapter.onCreateLastSeenViewHolder(parent);

src/org/thoughtcrime/securesms/util/StickyHeaderDecoration.java

@@ -127,7 +127,7 @@ public class StickyHeaderDecoration extends RecyclerView.ItemDecoration {
     }
   }
 
-  private int getHeaderTop(RecyclerView parent, View child, View header, int adapterPos,
+  protected int getHeaderTop(RecyclerView parent, View child, View header, int adapterPos,
                            int layoutPos)
   {
     int headerHeight = getHeaderHeightForLayout(header);
@@ -172,7 +172,7 @@ public class StickyHeaderDecoration extends RecyclerView.ItemDecoration {
     }
   }
 
-  private int getHeaderHeightForLayout(View header) {
+  protected int getHeaderHeightForLayout(View header) {
     return renderInline ? 0 : header.getHeight();
   }