Bug 1297117 - Make getUrlFromAboutReader private to avoid erronous usage r=sebastian

getUrlFromAboutReader can return null. There have been crashes caused by not checking this
result in the past. stripAboutReaderFromUrl is a safer version which returns the input URL
if necessary, and is probably what should be used in new code, hence we can make this method
private.

MozReview-Commit-ID: Lg7QWrpSE8F

--HG--
extra : histedit_source : 0964ebab8e9d66e65fc9c3a296031f720219f529

mobile/android/base/java/org/mozilla/gecko/reader/ReaderModeUtils.java

@@ -20,7 +20,7 @@ public class ReaderModeUtils {
      *     URLs.
      * @return <code>null</code> if the URL is malformed or doesn't contain a URL parameter.
      */
-    public static String getUrlFromAboutReader(String aboutReaderUrl) {
+    private static String getUrlFromAboutReader(String aboutReaderUrl) {
         return StringUtils.getQueryParameter(aboutReaderUrl, "url");
     }