[bfcache]Add new AILanguageDetector* classes and functions

This CL adds new AILanguageDetector/AILanguageDetectorFactory/
AILanguageDetectorCapabilities classes to match the new version of
API proposal[1].
Functions are mostly copied and pasted from the old version of the code.

[1] https://github.com/WICG/translation-api?tab=readme-ov-file#full-api-surface-in-web-idl

Bug: 349927087
Change-Id: I1eed4cb0d54e8388398aef642943c0d6a76857f1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5892958
Reviewed-by: Fergal Daly <[email protected]>
Commit-Queue: Yuzu Saijo <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1364800}

ai/language_detection/capabilities.tentative.window.js

@@ -0,0 +1,10 @@
+// META: title=capabilities test
+
+'use strict';
+
+promise_test(async t => {
+  const languageDetectorCapabilities = await ai.languageDetector.capabilities();
+  const availability = languageDetectorCapabilities.available;
+  assert_not_equals(availability, "no");
+  // TODO(crbug.com/349927087): Add languageDetectorCapabilities.canDetect("en") once implemented.
+});

ai/language_detection/detector.tentative.window.js

@@ -0,0 +1,14 @@
+// META: title=Detect english
+
+'use strict';
+
+promise_test(async t => {
+  const detector = await ai.languageDetector.create();
+  const results = await detector.detect("this string is in English");
+  // "en" should be highest confidence.
+  assert_equals(results[0].detectedLanguage, "en");
+  // Results should be from high to low confidence.
+  for (let i = 0; i < results.length - 1; i++) {
+    assert_greater_than_equal(results[i].confidence, results[i + 1].confidence);
+  }
+});