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/sms/DatabaseMessages.java

@@ -476,7 +476,7 @@ public class DatabaseMessages {
             mParts = new ArrayList<>();
             mPartsProcessed = false;
             for (int i = 0; i < nParts; i++) {
-                mParts.add((MmsPart) in.readParcelable(getClass().getClassLoader()));
+                mParts.add(in.readParcelable(getClass().getClassLoader()));
             }
         }