Ensure focus() gets called when navigating to text fields

This was a recent regression. Logic was added to make a top level editable a container (so that navigation would descend into it). However, we were previously using the container predicate to decide whether or not to set focus; this prevents focus() on roots which sometimes triggered other side effects such as focusing a descendant.

Make the focus precondition check the structuralContainer predicate instead.

BUG=640587
TEST=chromevox_tests

Review-Url: https://codereview.chromium.org/2273373002
Cr-Commit-Position: refs/heads/master@{#414871}

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

@@ -381,7 +381,7 @@ Background.prototype = {
       // Iframes, when focused, causes the child webArea to fire focus event.
       // This can result in getting stuck when navigating backward.
       if (actionNode.role != RoleType.iframe && !actionNode.state.focused &&
-          !AutomationPredicate.container(actionNode))
+          !AutomationPredicate.structuralContainer(actionNode))
         actionNode.focus();
     }
     var prevRange = this.currentRange_;

chrome/browser/resources/chromeos/chromevox/cvox2/background/background_test.extjs

@@ -1155,3 +1155,17 @@ TEST_F('BackgroundTest', 'EditableNavigation', function() {
         .replay();
   });
 });
+
+TEST_F('BackgroundTest', 'NavigationMovesFocus', function() {
+  this.runWithLoadedTree(function(root) {/*!
+    <p>start</p>
+    <input type="text"></input>
+  */}, function(root) {
+    this.listenOnce(root, 'focus', function(e) {
+      var focus = ChromeVoxState.instance.currentRange.start.node;
+      assertEquals(RoleType.textField, focus.role);
+      assertTrue(focus.state.focused);
+    });
+    doCmd('nextEditText')();
+  });
+});