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/android/support/v7/mms/DefaultApnSettingsLoader.java

@@ -290,7 +290,7 @@ class DefaultApnSettingsLoader implements ApnSettingsLoader {
         } else {
             uri = Telephony.Carriers.CONTENT_URI;
         }
-        Cursor cursor = null;
+        Cursor cursor;
         try {
             for (; ; ) {
                 // Try different combinations of queries. Some would work on some platforms.
@@ -448,7 +448,7 @@ class DefaultApnSettingsLoader implements ApnSettingsLoader {
             return addr;
         }
         final StringBuilder builder = new StringBuilder(16);
-        String result = null;
+        String result;
         for (int i = 0; i < 4; i++) {
             try {
                 if (octets[i].length() > 3) {