Set default lastStartTag in TokenizerTester

This change causes TokenizerTester to set a default lastStartTag value
for any test which has a initialStates value but no lastStartTag value.

Otherwise, without this change, the tokenizer is never actually run for
such missing-lastStartTag tests — which results in us failing 5 tests
from the html5lib-tests suite.

Author: sideshowbarker

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

@@ -140,18 +140,23 @@ private void runTest(JSONObject test) throws SAXException, IOException {
         } else {
             for (JSONValue value : contentModelFlags.getValue()) {
                 if (PCDATA.equals(value)) {
+                    lastStartTag = lastStartTag == null ? "xmp" : lastStartTag;
                     runTestInner(inputString, expectedTokens, description,
                             Tokenizer.DATA, lastStartTag);
                 } else if (RAWTEXT.equals(value)) {
+                    lastStartTag = lastStartTag == null ? "xmp" : lastStartTag;
                     runTestInner(inputString, expectedTokens, description,
                             Tokenizer.RAWTEXT, lastStartTag);
                 } else if (RCDATA.equals(value)) {
+                    lastStartTag = lastStartTag == null ? "xmp" : lastStartTag;
                     runTestInner(inputString, expectedTokens, description,
                             Tokenizer.RCDATA, lastStartTag);
                 } else if (CDATA.equals(value)) {
+                    lastStartTag = lastStartTag == null ? "xmp" : lastStartTag;
                     runTestInner(inputString, expectedTokens, description,
                             Tokenizer.CDATA_SECTION, lastStartTag);
                 } else if (PLAINTEXT.equals(value)) {
+                    lastStartTag = lastStartTag == null ? "plaintext" : lastStartTag;
                     runTestInner(inputString, expectedTokens, description,
                             Tokenizer.PLAINTEXT, lastStartTag);
                 } else if (SCRIPT_DATA.equals(value)) {