Refactor: Remove unused branch.

`filename` must be `null` at this point, as it's recently been set to that value, and hasn't adopted any other value yet. 

Refactoring change only. No functional changes intended.

Change-Id: I29a28872efc8c12c0da3c9f7c0a92d6aff465410

core/java/android/webkit/URLUtil.java

@@ -310,7 +310,7 @@ public final class URLUtil {
         String extension = null;
 
         // If we couldn't do anything with the hint, move toward the content disposition
-        if (filename == null && contentDisposition != null) {
+        if (contentDisposition != null) {
             filename = parseContentDisposition(contentDisposition);
             if (filename != null) {
                 int index = filename.lastIndexOf('/') + 1;