Add Charset.defaultCharset.

PiperOrigin-RevId: 355338816
Change-Id: I38c9e062b8d0a9391f913fc91ea17191bdeb757c

user/super/com/google/gwt/emul/java/nio/charset/Charset.java

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 e1af86e..aaa21e3 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
@@ -21,7 +21,6 @@
 import java.util.Collections;
 import java.util.SortedMap;
 import java.util.TreeMap;
-
 import javaemul.internal.EmulatedCharset;
 import javaemul.internal.NativeRegExp;
 
@@ -45,6 +44,10 @@
     return AvailableCharsets.CHARSETS;
   }
 
+  public static Charset defaultCharset() {
+    return EmulatedCharset.UTF_8;
+  }
+
   public static Charset forName(String charsetName) {
     checkArgument(charsetName != null, "Null charset name");