Fix obscure TreeMap instantiation in Charset.

Change-Id: I920911edc367b7b6f1f958b76dab6b526188345d
diff --git a/user/super/com/google/gwt/emul/java/nio/charset/Charset.java b/user/super/com/google/gwt/emul/java/nio/charset/Charset.java
index 1c70857..0025e82 100644
--- a/user/super/com/google/gwt/emul/java/nio/charset/Charset.java
+++ b/user/super/com/google/gwt/emul/java/nio/charset/Charset.java
@@ -33,7 +33,7 @@
   private static final class AvailableCharsets {
     private static final SortedMap<String, Charset> CHARSETS;
     static {
-      SortedMap<String, Charset> map = new TreeMap<String, Charset>() { };
+      SortedMap<String, Charset> map = new TreeMap<>();
       map.put(EmulatedCharset.ISO_8859_1.name(), EmulatedCharset.ISO_8859_1);
       map.put(EmulatedCharset.ISO_LATIN_1.name(), EmulatedCharset.ISO_LATIN_1);
       map.put(EmulatedCharset.UTF_8.name(), EmulatedCharset.UTF_8);