Text Encoding: Convert fast/encoding tests to testharness.js

third_party/WebKit/LayoutTests/fast/encoding/resources/char-decoding-utils.js

-function decodeText(charsetName, characterSequence)
-{
-    var req = new XMLHttpRequest;
-    req.open('GET', 'data:text/plain,' + characterSequence, false);
-    req.overrideMimeType('text/plain; charset="' + charsetName + '"');
+function decodeText(charsetName, characterSequence) {

[foolip, 2016/10/04 09:35:18]

Can't this use https://encoding.spec.whatwg.org/#interface-textdecoder? Is the
concern that XHR and the API might use different code paths? If so test both?

[jsbell, 2016/10/04 17:41:39]

They do differ. :( Specifically the API flushes at the end of a stream, other
cases do not.

Agreed that we should have tests that cover all encodings via all methods of
doing encode/decode (e.g. API, XHR, forms/URL, ...). On the to-do list, probably
as a follow on to the big i18n test upstreaming. Tracked as
https://bugs.chromium.org/p/chromium/issues/detail?id=409992

+  return new Promise((resolve, reject) => {
+    const req = new XMLHttpRequest;
+    req.open('GET', `data:text/plain,${characterSequence}`, /*async*/true);

[foolip, 2016/10/04 09:35:18]

async is the default, omit? (It helps understand this CL, but not really
afterwards.)

[jsbell, 2016/10/04 17:41:39]

Done.

+    req.overrideMimeType(`text/plain; charset="${charsetName}"`);
     req.send('');
-    return req.responseText;
+    req.onload = e => resolve(req.responseText);
+    req.onerror = e => reject(new Error(req.statusText));
+  });
 }
 
-function decode(charsetName, characterSequence)
-{
-    var decodedText = decodeText(charsetName, characterSequence);
-    var result = "";
-    for (var i = 0; i < decodedText.length; ++i) {
-        var code = decodedText.charCodeAt(i).toString(16).toUpperCase();
-        if (i)
-            result += "/";
-        result += "U+" + ("0000" + code).slice(-4);
-    }
-    return result;
+function decode(charsetName, characterSequence) {
+  return decodeText(charsetName, characterSequence).then(decodedText => {
+    return decodedText.split('')
+      .map(char => char.charCodeAt(0))
+      .map(code => 'U+' + ('0000' + code.toString(16).toUpperCase()).slice(-4))
+      .join('/');
+  });
 }
 
-function testDecode(charsetName, characterSequence, unicode)
-{
-    shouldBe("decode('" + charsetName + "', '" + characterSequence + "')", "'" + unicode + "'");
+function testDecode(charsetName, characterSequence, unicode) {
+  promise_test(t => {
+    return decode(charsetName, characterSequence).then(result => {
+      assert_equals(result, unicode);
+    });
+  }, `Decode ${charsetName}: ${characterSequence} => ${unicode}`);
 }
 
-function batchTestDecode(inputData)
-{
-    for (var i in inputData.encodings) {
-        for (var j in inputData.encoded)
-            testDecode(inputData.encodings[i], inputData.encoded[j], inputData.unicode[j]);
+function batchTestDecode(inputData) {
+  for (let i in inputData.encodings) {
+    for (let j in inputData.encoded) {
+      testDecode(inputData.encodings[i],
+                 inputData.encoded[j],
+                 inputData.unicode[j]);
     }
+  }
 }