Messaging: Further code improvements

* Remove redundant casts
* getParcelable(ArrayList|Exra) without class argument is deprecated
* ViewPager.setOnPageChangeListener -> addOnPageChangeListener
* RecyclerView.setOnScrollListener -> addOnScrollListener
* Remove unused initializations
* Remove unused code

Change-Id: I21beb6c90c675a4f2cfd7e3d5ebbd18b745f5911

src/com/android/messaging/datamodel/media/DecodedImageResource.java

@@ -220,7 +220,6 @@ public class DecodedImageResource extends ImageResource {
             } finally {
                 if (scaledBitmap != null && scaledBitmap != getBitmap()) {
                     scaledBitmap.recycle();
-                    scaledBitmap = null;
                 }
                 releaseLock();
                 release();