android: Make member final

Change-Id: I61e6b512120df15c81c8c22ed2a97c38ca0813f7
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/194196
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

android/source/src/java/org/mozilla/gecko/gfx/DisplayPortCalculator.java

@@ -20,7 +20,7 @@ final class DisplayPortCalculator {
     // Keep this in sync with the TILEDLAYERBUFFER_TILE_SIZE defined in gfx/layers/TiledLayerBuffer.h
     private static final int TILE_SIZE = 256;
 
-    private DisplayPortStrategy sStrategy;
+    private final DisplayPortStrategy sStrategy;
 
     DisplayPortCalculator(LibreOfficeMainActivity context) {
         sStrategy = new VelocityBiasStrategy(context);