ChromeVox: Language switching test infrastructure clean up.

This does two things:
1. Cleans up the language switching code to use consistent terms. Most
notably, it changes all instances of "inner-node switching" to
"sub-node switching".
2. Cleans up the language switching test infrastructure. A test
naming scheme was implemented to easily communicate the purpose of
each test. Also, tests were added to cover the two language switching
behaviors: node-level and sub-node-level switching. Each document
in the test databank is tested using node-level and sub-node-level
switching.

Bug: 923068
Change-Id: Ia16b785381966d97e089aae5dc08e23173876d08
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1754703
Commit-Queue: Akihiro Ota <akihiroota@chromium.org>
Reviewed-by: Alice Boxhall <aboxhall@chromium.org>
Reviewed-by: Chris Hall <chrishall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#690998}

chrome/browser/resources/chromeos/chromevox/cvox2/background/language_switching.js

@@ -5,29 +5,30 @@
 /**
  * @fileoverview Provides language switching services for ChromeVox, which
  * uses language detection information to automatically change the ChromeVox
- * output language.
+ * output voice.
  */
 
 goog.provide('LanguageSwitching');
 
 /**
  * The current output language. Initialize to the language of the browser or
- * empty string if unavailable.
+ * empty string if the former is unavailable.
  * @private {string}
  */
 LanguageSwitching.currentLanguage_ =
     chrome.i18n.getUILanguage().toLowerCase() || '';
 
 /**
- * Confidence threshold to meet before assigning inner-node language.
+ * Confidence threshold to meet before assigning sub-node language.
  * @const
  * @private {number}
  */
-LanguageSwitching.PROBABILITY_THRESHOLD = 0.9;
+LanguageSwitching.PROBABILITY_THRESHOLD_ = 0.9;
 
 /**
- * Stores whether or not ChromeVox inner-node language switching is enabled or
- * disabled.
+ * Stores whether or not ChromeVox sub-node language switching is enabled.
+ * Set to false as default, as sub-node language detection is still
+ * experimental.
  * @private {boolean}
  */
 LanguageSwitching.sub_node_switching_enabled_ = false;
@@ -36,8 +37,7 @@ LanguageSwitching.sub_node_switching_enabled_ = false;
  * Initialization function for language switching.
  */
 LanguageSwitching.init = function() {
-  // Enable inner-node language switching if inner-node switching feature flag
-  // is enabled.
+  // Enable sub-node language switching if feature flag is enabled.
   chrome.commandLinePrivate.hasSwitch(
       'enable-experimental-accessibility-chromevox-sub-node-language-' +
           'switching',
@@ -64,7 +64,6 @@ LanguageSwitching.assignLanguagesForStringAttribute = function(
     return;
   var stringAttributeValue = node[stringAttribute];
   var languageAnnotation;
-
   // Quick note:
   // The decideNewLanguage function, which contains the core language switching
   // logic, is setup to prefer sub-node switching if the detected language's
@@ -74,18 +73,10 @@ LanguageSwitching.assignLanguagesForStringAttribute = function(
     languageAnnotation =
         node.languageAnnotationForStringAttribute(stringAttribute);
   } else {
-    // Use node-level language switching if inner-node switching is
-    // disabled. We use this logic because the API is disabled when sub-node
-    // switching is disabled.
     var nodeLevelLanguageData = {};
     // Ensure that we span the entire stringAttributeValue.
     nodeLevelLanguageData.startIndex = 0;
     nodeLevelLanguageData.endIndex = stringAttributeValue.length;
-    // To force the decideNewLanguage function to use node-level switching, we
-    // pass in an empty language with probability that doesn't exceed the
-    // PROBABILITY_THRESHOLD. As previously mentioned, if we are not confident
-    // enough in inner-node detected languages, we fall back on node-level
-    // language.
     nodeLevelLanguageData.language = '';
     nodeLevelLanguageData.probability = 0;
     languageAnnotation = [nodeLevelLanguageData];
@@ -100,9 +91,10 @@ LanguageSwitching.assignLanguagesForStringAttribute = function(
         stringAttributeValue || '', LanguageSwitching.currentLanguage_);
     return;
   }
+
   // Split output based on language annotation.
   // Each object in languageAnnotation contains a language, probability,
-  // and start/end indices that define a substring.
+  // and start/end indices that define a substring of stringAttributeValue.
   for (var i = 0; i < languageAnnotation.length; ++i) {
     var speechProps = new Output.SpeechProperties();
     var startIndex = languageAnnotation[i].startIndex;
@@ -130,14 +122,14 @@ LanguageSwitching.assignLanguagesForStringAttribute = function(
 /**
  * Run error checks on language data and decide new output language.
  * @param {!AutomationNode} node
- * @param {string} innerNodeLanguage
+ * @param {string} subNodeLanguage
  * @param {number} probability
  * @return {string}
  */
 LanguageSwitching.decideNewLanguage = function(
-    node, innerNodeLanguage, probability) {
+    node, subNodeLanguage, probability) {
   // Use the following priority rankings when deciding language.
-  // 1. Inner-node language. If we can detect inner-node language with a high
+  // 1. Sub-node language. If we can detect sub-node language with a high
   // enough probability of accuracy, then we should use it.
   // 2. Node-level detected language.
   // 3. Author-provided language. This language is also assigned at the node
@@ -145,9 +137,9 @@ LanguageSwitching.decideNewLanguage = function(
   // 4. LanguageSwitching.currentLanguage_. If we do not have enough language
   // data, then we should not switch languages.
 
-  // Use innerNodeLanguage if probability exceeds threshold.
-  if (probability > LanguageSwitching.PROBABILITY_THRESHOLD)
-    return innerNodeLanguage.toLowerCase();
+  // Use subNodeLanguage if probability exceeds threshold.
+  if (probability > LanguageSwitching.PROBABILITY_THRESHOLD_)
+    return subNodeLanguage.toLowerCase();
 
   // Use detected language as nodeLevelLanguage, if present.
   // If no detected language, use author-provided language.
@@ -181,7 +173,7 @@ LanguageSwitching.decideNewLanguage = function(
 };
 
 /**
- * Returns a unicode-aware substring of text from startIndex to endIndex.
+ * Returns a unicode-aware substring of |text| from startIndex to endIndex.
  * @param {string} text
  * @param {number} startIndex
  * @param {number} endIndex