Removing @Nullable for functions which cannot return null

Patch is removing keyword for void-returning function
and function returning primitive type

Bug: 
Change-Id: I4ad9df4c76aeea1e2c488facaa5f40e378f455d3
Reviewed-on: https://chromium-review.googlesource.com/802154
Commit-Queue: Ted Choc <tedchoc@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Reviewed-by: Derek Cheng <imcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#520755}

chrome/android/java/src/org/chromium/chrome/browser/locale/DefaultSearchEnginePromoDialog.java

@@ -123,7 +123,6 @@ public class DefaultSearchEnginePromoDialog extends PromoDialog {
 
     /** See {@link #sObserver}. */
     @VisibleForTesting
-    @Nullable
     public static void setObserverForTests(DefaultSearchEnginePromoDialogObserver observer) {
         sObserver = observer;
     }

chrome/android/java/src/org/chromium/chrome/browser/media/router/cast/CastMediaRouteProvider.java

@@ -451,7 +451,6 @@ public class CastMediaRouteProvider implements MediaRouteProvider, DiscoveryDele
         mMessageHandler = new CastMessageHandler(this);
     }
 
-    @Nullable
     private boolean canAutoJoin(MediaSource source, String origin, int tabId) {
         if (source.getAutoJoinPolicy().equals(MediaSource.AUTOJOIN_PAGE_SCOPED)) return false;