Add a page to explain earcons in the tutorial

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

Index: chrome/browser/resources/chromeos/chromevox/cvox2/background/background.js
diff --git a/chrome/browser/resources/chromeos/chromevox/cvox2/background/background.js b/chrome/browser/resources/chromeos/chromevox/cvox2/background/background.js
index dc2fdece34394575665044b27b4eea25786baba3..b120e2abcbfc4705f984b0665212a5f11b26d59e 100644
--- a/chrome/browser/resources/chromeos/chromevox/cvox2/background/background.js
+++ b/chrome/browser/resources/chromeos/chromevox/cvox2/background/background.js
@@ -786,11 +786,13 @@ Background.prototype = {
     }
 
     // Next, try to focus the start or end node.
-    if (isFocusableLinkOrControl(start)) {
+    if (!AutomationPredicate.structuralContainer(start) &&
+        start.state.focusable) {
       if (!start.state.focused)
         start.focus();
       return;
-    } else if (isFocusableLinkOrControl(end)) {
+    } else if (!AutomationPredicate.structuralContainer(end) &&
+        end.state.focusable) {
       if (!end.state.focused)
         end.focus();
       return;