Update resize handle for new designs

The diff should have information on what this does and how it is supposed to work.

src/stores/room-list/ListLayout.ts

@@ -52,7 +52,24 @@ export class ListLayout {
     }
 
     public get minVisibleTiles(): number {
-        return 3;
+        // the .65 comes from the CSS where the show more button is
+        // mathematically 65% of a tile when floating.
+        return 4.65;
+    }
+
+    public calculateTilesToPixelsMin(maxTiles: number, n: number, possiblePadding: number): number {
+        // Only apply the padding if we're about to use maxTiles as we need to
+        // plan for the padding. If we're using n, the padding is already accounted
+        // for by the resizing stuff.
+        let padding = 0;
+        if (maxTiles < n) {
+            padding = possiblePadding;
+        }
+        return this.tilesToPixels(Math.min(maxTiles, n)) + padding;
+    }
+
+    public tilesToPixelsWithPadding(n: number, padding: number): number {
+        return this.tilesToPixels(n) + padding;
     }
 
     public tilesToPixels(n: number): number {