Add new EncodingPrescanTester class

This change adds a new EncodingPrescanTester class, the purpose of which
is to test the output of running just the meta prescan on test data —
that is, when the expected result is limited to what can be determined
by checking only the first 1024 bytes of the input stream.

test-src/nu/validator/htmlparser/test/EncodingPrescanTester.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2020 Mozilla Foundation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+package nu.validator.htmlparser.test;
+
+import java.io.InputStream;
+
+public class EncodingPrescanTester extends EncodingTester {
+
+    static {
+        SNIFFING_LIMIT = 1024;
+    }
+
+    public EncodingPrescanTester(InputStream aggregateStream) {
+        super(aggregateStream);
+    }
+
+}