Refactor SwitchAccess to use same TreeWalker as CVox

Bug: 873016
Change-Id: If8ee78b9e739aaad0403964948534c3305b26580
Reviewed-on: https://chromium-review.googlesource.com/1170383Reviewed-by: David Tseng <dtseng@chromium.org>
Commit-Queue: Zach Helfinstein <zhelfins@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582169}

chrome/browser/resources/chromeos/chromevox/BUILD.gn

@@ -7,6 +7,7 @@ import("//chrome/common/features.gni")
 import("//components/nacl/features.gni")
 import("//testing/test.gni")
 import("//chrome/test/base/js2gtest.gni")
+import("//third_party/closure_compiler/compile_js.gni")
 import("run_jsbundler.gni")
 
 assert(is_chromeos)
@@ -643,3 +644,36 @@ js2gtest("chromevox_extjs_tests") {
   ]
   defines = [ "HAS_OUT_OF_PROC_TEST_RUNNER" ]
 }
+
+js_library("tree_walker") {
+  sources = [
+    "cvox2/background/tree_walker.js",
+  ]
+  deps = [
+    ":automation_predicate",
+    ":constants",
+  ]
+  externs_list = [
+    "$externs_path/automation.js",
+    "$externs_path/chrome_extensions.js",
+  ]
+}
+
+js_library("automation_predicate") {
+  sources = [
+    "cvox2/background/automation_predicate.js",
+  ]
+  deps = [
+    ":constants",
+  ]
+  externs_list = [
+    "$externs_path/automation.js",
+    "$externs_path/chrome_extensions.js",
+  ]
+}
+
+js_library("constants") {
+  sources = [
+    "cvox2/background/constants.js",
+  ]
+}

chrome/browser/resources/chromeos/switch_access/BUILD.gn

@@ -26,9 +26,11 @@ run_jsbundler("switch_access_copied_files") {
   mode = "copy"
   dest_dir = switch_access_dir
   sources = [
+    "../chromevox/cvox2/background/constants.js",
+    "../chromevox/cvox2/background/tree_walker.js",
+    "../select_to_speak/closure_shim.js",
     "auto_scan_manager.js",
     "automation_manager.js",
-    "automation_predicate.js",
     "background.js",
     "commands.js",
     "keyboard_handler.js",
@@ -37,11 +39,13 @@ run_jsbundler("switch_access_copied_files") {
     "options.js",
     "prefs.js",
     "switch_access.js",
-    "tree_walker.js",
+    "switch_access_predicate.js",
   ]
   rewrite_rules = [
     rebase_path(".", root_build_dir) + ":",
     rebase_path(closure_library_dir, root_build_dir) + ":closure",
+    rebase_path("../chromevox/cvox2/background", root_build_dir) + ":",
+    rebase_path("../select_to_speak", root_build_dir) + ":",
   ]
 }
 
@@ -56,14 +60,12 @@ js2gtest("switch_access_webuijs_tests") {
   test_type = "webui"
   sources = [
     "auto_scan_manager_unittest.gtestjs",
-    "automation_predicate_unittest.gtestjs",
-    "tree_walker_unittest.gtestjs",
+    "switch_access_predicate_unittest.gtestjs",
   ]
   extra_js_files = [
     "auto_scan_manager.js",
-    "automation_predicate.js",
+    "switch_access_predicate.js",
     "test_support.js",
-    "tree_walker.js",
   ]
   defines = [ "HAS_OUT_OF_PROC_TEST_RUNNER" ]
 }
@@ -113,16 +115,18 @@ js_type_check("closure_compile") {
   deps = [
     ":auto_scan_manager",
     ":automation_manager",
-    ":automation_predicate",
     ":background",
     ":commands",
     ":keyboard_handler",
     ":options",
     ":prefs",
+    ":switch_access_predicate",
+    "../chromevox:constants",
+    "../chromevox:tree_walker",
+    "../select_to_speak:closure_shim",
 
     # ":switch_access",
     ":switch_access_interface",
-    ":tree_walker",
   ]
 }
 
@@ -134,8 +138,9 @@ js_library("auto_scan_manager") {
 
 js_library("automation_manager") {
   deps = [
-    ":automation_predicate",
-    ":tree_walker",
+    ":switch_access_predicate",
+    "../chromevox:constants",
+    "../chromevox:tree_walker",
   ]
   externs_list = [
     "$externs_path/accessibility_private.js",
@@ -143,7 +148,7 @@ js_library("automation_manager") {
   ]
 }
 
-js_library("automation_predicate") {
+js_library("switch_access_predicate") {
   externs_list = [ "$externs_path/automation.js" ]
 }
 
@@ -198,7 +203,3 @@ js_library("switch_access") {
 
 js_library("switch_access_interface") {
 }
-
-js_library("tree_walker") {
-  externs_list = [ "$externs_path/automation.js" ]
-}

chrome/browser/resources/chromeos/switch_access/automation_manager.js

@@ -40,13 +40,6 @@ function AutomationManager(desktop) {
    */
   this.scopeStack_ = [];
 
-  /**
-   * Moves to the appropriate node in the accessibility tree.
-   *
-   * @private {!AutomationTreeWalker}
-   */
-  this.treeWalker_ = this.createTreeWalker_(desktop);
-
   this.init_();
 }
 
@@ -102,10 +95,9 @@ AutomationManager.prototype = {
 
     // Move to focused node.
     this.node_ = event.target;
-    this.treeWalker_ = this.createTreeWalker_(this.scope_, this.node_);
 
     // In case the node that gained focus is not a subtreeLeaf.
-    if (AutomationPredicate.isSubtreeLeaf(this.node_, this.scope_)) {
+    if (SwitchAccessPredicate.isSubtreeLeaf(this.node_, this.scope_)) {
       this.printNode_(this.node_);
       this.updateFocusRing_();
     } else
@@ -135,7 +127,7 @@ AutomationManager.prototype = {
       let ancestor = ancestorList.pop();
       if (ancestor.role === chrome.automation.RoleType.DESKTOP)
         continue;
-      if (AutomationPredicate.isGroup(ancestor, this.scope_)) {
+      if (SwitchAccessPredicate.isGroup(ancestor, this.scope_)) {
         this.scopeStack_.push(this.scope_);
         this.scope_ = ancestor;
       }
@@ -189,12 +181,24 @@ AutomationManager.prototype = {
     // If node is invalid, set node to last valid scope.
     this.startAtValidNode_();
 
-    let node = this.treeWalker_.moveToNode(doNext);
-    if (node) {
-      this.node_ = node;
-      this.printNode_(this.node_);
-      this.updateFocusRing_();
+    let treeWalker = new AutomationTreeWalker(
+        this.node_, doNext ? constants.Dir.FORWARD : constants.Dir.BACKWARD,
+        SwitchAccessPredicate.restrictions(this.scope_));
+
+    let node = treeWalker.next().node;
+
+    // If treeWalker returns undefined, that means we're at the end of the tree
+    // and we should start over.
+    if (!node) {
+      if (doNext)
+        node = this.scope_;
+      else
+        node = this.youngestDescendant_(this.scope_);
     }
+
+    this.node_ = node;
+    this.printNode_(this.node_);
+    this.updateFocusRing_();
   },
 
   /**
@@ -220,17 +224,15 @@ AutomationManager.prototype = {
         this.scope_ = this.scopeStack_.pop();
       } while (!this.scope_.role && this.scopeStack_.length > 0);
 
-      this.treeWalker_ = this.createTreeWalker_(this.scope_, this.node_);
       this.updateFocusRing_();
       console.log('Moved to previous scope');
       this.printNode_(this.node_);
       return;
     }
 
-    if (AutomationPredicate.isGroup(this.node_, this.scope_)) {
+    if (SwitchAccessPredicate.isGroup(this.node_, this.scope_)) {
       this.scopeStack_.push(this.scope_);
       this.scope_ = this.node_;
-      this.treeWalker_ = this.createTreeWalker_(this.scope_);
       console.log('Entered scope');
       this.moveToNode(true);
       return;
@@ -250,7 +252,7 @@ AutomationManager.prototype = {
     let color;
     if (this.node_ === this.scope_)
       color = AutomationManager.Color.SCOPE;
-    else if (AutomationPredicate.isGroup(this.node_, this.scope_))
+    else if (SwitchAccessPredicate.isGroup(this.node_, this.scope_))
       color = AutomationManager.Color.GROUP;
     else
       color = AutomationManager.Color.LEAF;
@@ -281,36 +283,6 @@ AutomationManager.prototype = {
       this.node_ = this.scopeStack_.pop();
       this.scope_ = this.node_;
     }
-    this.treeWalker_ = this.createTreeWalker_(this.scope_);
-  },
-
-  /**
-   * Create an AutomationTreeWalker for the subtree with |scope| as its root.
-   * If |opt_start| is defined, the tree walker will start walking the tree
-   * from |opt_start|; otherwise, it will start from |scope|.
-   *
-   * @param {!chrome.automation.AutomationNode} scope
-   * @param {!chrome.automation.AutomationNode=} opt_start
-   * @private
-   * @return {!AutomationTreeWalker}
-   */
-  createTreeWalker_: function(scope, opt_start) {
-    // If no explicit start node, start walking the tree from |scope|.
-    let start = opt_start || scope;
-
-    let leafPred = function(node) {
-      return (node !== scope &&
-              AutomationPredicate.isSubtreeLeaf(node, scope)) ||
-          !AutomationPredicate.isInterestingSubtree(node);
-    };
-    let visitPred = function(node) {
-      // Avoid visiting the top-level root node (i.e., the desktop node).
-      return node !== this.desktop_ &&
-          AutomationPredicate.isSubtreeLeaf(node, scope);
-    }.bind(this);
-
-    let restrictions = {leaf: leafPred, visit: visitPred};
-    return new AutomationTreeWalker(start, scope, restrictions);
   },
 
   // TODO(elichtenberg): Move print functions to a custom logger class. Only
@@ -343,50 +315,19 @@ AutomationManager.prototype = {
   },
 
   /**
-   * Move to the next sibling of this.node_ if it has one.
-   */
-  debugMoveToNext: function() {
-    let next = this.treeWalker_.debugMoveToNext(this.node_);
-    if (next) {
-      this.node_ = next;
-      this.printNode_(this.node_);
-      chrome.accessibilityPrivate.setFocusRing([this.node_.location]);
-    }
-  },
-
-  /**
-   * Move to the previous sibling of this.node_ if it has one.
+   * Get the youngest descendant of |node|, if it has one within the current
+   * scope.
+   *
+   * @param {!chrome.automation.AutomationNode} node
+   * @return {!chrome.automation.AutomationNode}
+   * @private
    */
-  debugMoveToPrevious: function() {
-    let prev = this.treeWalker_.debugMoveToPrevious(this.node_);
-    if (prev) {
-      this.node_ = prev;
-      this.printNode_(this.node_);
-      chrome.accessibilityPrivate.setFocusRing([this.node_.location]);
-    }
-  },
+  youngestDescendant_: function(node) {
+    let leaf = SwitchAccessPredicate.leaf(this.scope_);
 
-  /**
-   * Move to the first child of this.node_ if it has one.
-   */
-  debugMoveToFirstChild: function() {
-    let child = this.treeWalker_.debugMoveToFirstChild(this.node_);
-    if (child) {
-      this.node_ = child;
-      this.printNode_(this.node_);
-      chrome.accessibilityPrivate.setFocusRing([this.node_.location]);
-    }
-  },
+    while (node.lastChild && !leaf(node))
+      node = node.lastChild;
 
-  /**
-   * Move to the parent of this.node_ if it has one.
-   */
-  debugMoveToParent: function() {
-    let parent = this.treeWalker_.debugMoveToParent(this.node_);
-    if (parent) {
-      this.node_ = parent;
-      this.printNode_(this.node_);
-      chrome.accessibilityPrivate.setFocusRing([this.node_.location]);
-    }
+    return node;
   }
 };

chrome/browser/resources/chromeos/switch_access/commands.js

@@ -78,24 +78,6 @@ Commands.prototype = {
       'options': {
         'defaultKeyCode': 52, /* '4' key */
         'binding': this.switchAccess_.showOptionsPage.bind(this.switchAccess_)
-      },
-      'debugNext': {
-        'defaultKeyCode': -1, /* unused key */
-        'binding': this.switchAccess_.debugMoveToNext.bind(this.switchAccess_)
-      },
-      'debugPrevious': {
-        'defaultKeyCode': -1, /* unused key */
-        'binding':
-            this.switchAccess_.debugMoveToPrevious.bind(this.switchAccess_)
-      },
-      'debugChild': {
-        'defaultKeyCode': -1, /* unused key */
-        'binding':
-            this.switchAccess_.debugMoveToFirstChild.bind(this.switchAccess_)
-      },
-      'debugParent': {
-        'defaultKeyCode': -1, /* unused key */
-        'binding': this.switchAccess_.debugMoveToParent.bind(this.switchAccess_)
       }
     };
   }

chrome/browser/resources/chromeos/switch_access/manifest.json.jinja2

@@ -13,8 +13,10 @@
     "scripts": [
       "auto_scan_manager.js",
       "automation_manager.js",
-      "automation_predicate.js",
+      "switch_access_predicate.js",
+      "closure_shim.js",
       "commands.js",
+      "constants.js",
       "keyboard_handler.js",
       "prefs.js",
       "switch_access.js",

chrome/browser/resources/chromeos/switch_access/switch_access.js

@@ -224,45 +224,5 @@ SwitchAccess.prototype = {
    */
   keyCodeIsUsed: function(keyCode) {
     return this.switchAccessPrefs_.keyCodeIsUsed(keyCode);
-  },
-
-  /**
-   * Move to the next sibling of the current node if it has one.
-   *
-   * @override
-   */
-  debugMoveToNext: function() {
-    if (this.automationManager_)
-      this.automationManager_.debugMoveToNext();
-  },
-
-  /**
-   * Move to the previous sibling of the current node if it has one.
-   *
-   * @override
-   */
-  debugMoveToPrevious: function() {
-    if (this.automationManager_)
-      this.automationManager_.debugMoveToPrevious();
-  },
-
-  /**
-   * Move to the first child of the current node if it has one.
-   *
-   * @override
-   */
-  debugMoveToFirstChild: function() {
-    if (this.automationManager_)
-      this.automationManager_.debugMoveToFirstChild();
-  },
-
-  /**
-   * Move to the parent of the current node if it has one.
-   *
-   * @override
-   */
-  debugMoveToParent: function() {
-    if (this.automationManager_)
-      this.automationManager_.debugMoveToParent();
   }
 };

chrome/browser/resources/chromeos/switch_access/switch_access_interface.js

@@ -99,25 +99,5 @@ SwitchAccessInterface.prototype = {
    * @param {number} keyCode
    * @return {boolean}
    */
-  keyCodeIsUsed: function(keyCode) {},
-
-  /**
-   * Move to the next sibling of the current node if it has one.
-   */
-  debugMoveToNext: function() {},
-
-  /**
-   * Move to the previous sibling of the current node if it has one.
-   */
-  debugMoveToPrevious: function() {},
-
-  /**
-   * Move to the first child of the current node if it has one.
-   */
-  debugMoveToFirstChild: function() {},
-
-  /**
-   * Move to the parent of the current node if it has one.
-   */
-  debugMoveToParent: function() {}
+  keyCodeIsUsed: function(keyCode) {}
 };

chrome/browser/resources/chromeos/switch_access/automation_predicate.js → chrome/browser/resources/chromeos/switch_access/switch_access_predicate.js

@@ -8,19 +8,75 @@
  *
  * @constructor
  */
-function AutomationPredicate() {}
+function SwitchAccessPredicate() {}
 
 /**
- * Returns true if |node| is a subtreeLeaf, meaning that |node| is either
- * interesting or a group (both defined below).
+ * Returns a Restrictions object ready to be passed to AutomationTreeWalker.
+ *
+ * @param {!chrome.automation.AutomationNode} scope
+ * @return {!AutomationTreeWalkerRestriction}
+ */
+SwitchAccessPredicate.restrictions = function(scope) {
+  return {
+    leaf: SwitchAccessPredicate.leaf(scope),
+    root: SwitchAccessPredicate.root(scope),
+    visit: SwitchAccessPredicate.visit(scope)
+  };
+};
+
+/**
+ * Creates a function that confirms if |node| is a terminal leaf node of a
+ * SwitchAccess scope tree when |scope| is the root.
+ *
+ * @param {!chrome.automation.AutomationNode} scope
+ * @return {function(!chrome.automation.AutomationNode): boolean}
+ */
+SwitchAccessPredicate.leaf = function(scope) {
+  return function(node) {
+    return (node !== scope &&
+            SwitchAccessPredicate.isSubtreeLeaf(node, scope)) ||
+        !SwitchAccessPredicate.isInterestingSubtree(node);
+  }.bind(scope);
+};
+
+/**
+ * Creates a function that confirms if |node| is the root of a SwitchAccess
+ * scope tree when |scope| is the root.
+ *
+ * @param {!chrome.automation.AutomationNode} scope
+ * @return {function(!chrome.automation.AutomationNode): boolean}
+ */
+SwitchAccessPredicate.root = function(scope) {
+  return function(node) {
+    return node === scope;
+  }.bind(scope);
+};
+
+/**
+ * Creates a function that determines whether |node| is to be visited in the
+ * SwitchAccess scope tree with |scope| as the root.
+ *
+ * @param {!chrome.automation.AutomationNode} scope
+ * @return {function(!chrome.automation.AutomationNode): boolean}
+ */
+SwitchAccessPredicate.visit = function(scope) {
+  return function(node) {
+    return node.role !== chrome.automation.RoleType.DESKTOP &&
+        SwitchAccessPredicate.isSubtreeLeaf(node, scope);
+  }.bind(scope);
+};
+
+/**
+ * Returns true if |node| is a subtreeLeaf, meaning that |node|
+ * is either interesting or a group (both defined below).
  *
  * @param {!chrome.automation.AutomationNode} node
  * @param {!chrome.automation.AutomationNode} scope
  * @return {boolean}
  */
-AutomationPredicate.isSubtreeLeaf = function(node, scope) {
-  return AutomationPredicate.isActionable(node) ||
-      AutomationPredicate.isGroup(node, scope);
+SwitchAccessPredicate.isSubtreeLeaf = function(node, scope) {
+  return SwitchAccessPredicate.isActionable(node) ||
+      SwitchAccessPredicate.isGroup(node, scope);
 };
 
 /**
@@ -35,8 +91,8 @@ AutomationPredicate.isSubtreeLeaf = function(node, scope) {
  * @param {!chrome.automation.AutomationNode} scope
  * @return {boolean}
  */
-AutomationPredicate.isGroup = function(node, scope) {
-  if (node !== scope && AutomationPredicate.hasSameLocation_(node, scope))
+SwitchAccessPredicate.isGroup = function(node, scope) {
+  if (node !== scope && SwitchAccessPredicate.hasSameLocation_(node, scope))
     return false;
 
   // Work around for client nested in client. No need to have user select both
@@ -49,7 +105,7 @@ AutomationPredicate.isGroup = function(node, scope) {
   let interestingBranches = 0;
   let children = node.children || [];
   for (let child of children) {
-    if (AutomationPredicate.isInterestingSubtree(child))
+    if (SwitchAccessPredicate.isInterestingSubtree(child))
       interestingBranches += 1;
     if (interestingBranches > 1)
       return true;
@@ -64,7 +120,7 @@ AutomationPredicate.isGroup = function(node, scope) {
  * @param {!chrome.automation.AutomationNode} node2
  * @return {boolean}
  */
-AutomationPredicate.hasSameLocation_ = function(node1, node2) {
+SwitchAccessPredicate.hasSameLocation_ = function(node1, node2) {
   let l1 = node1.location;
   let l2 = node2.location;
   return l1.left === l2.left && l1.top === l2.top && l1.width === l2.width &&
@@ -78,10 +134,10 @@ AutomationPredicate.hasSameLocation_ = function(node1, node2) {
  * @param {!chrome.automation.AutomationNode} node
  * @return {boolean}
  */
-AutomationPredicate.isInterestingSubtree = function(node) {
+SwitchAccessPredicate.isInterestingSubtree = function(node) {
   let children = node.children || [];
-  return AutomationPredicate.isActionable(node) ||
-      children.some(AutomationPredicate.isInterestingSubtree);
+  return SwitchAccessPredicate.isActionable(node) ||
+      children.some(SwitchAccessPredicate.isInterestingSubtree);
 };
 
 /**
@@ -91,7 +147,7 @@ AutomationPredicate.isInterestingSubtree = function(node) {
  * @param {!chrome.automation.AutomationNode} node
  * @return {boolean}
  */
-AutomationPredicate.isActionable = function(node) {
+SwitchAccessPredicate.isActionable = function(node) {
   let loc = node.location;
   let parent = node.parent;
   let root = node.root;

chrome/browser/resources/chromeos/switch_access/tree_walker.js

-// Copyright 2017 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-/**
- * Class to move to the appropriate node in the accessibility tree. Stays in a
- * subtree determined by restrictions passed to it.
- *
- * @constructor
- * @param {!chrome.automation.AutomationNode} start
- * @param {!chrome.automation.AutomationNode} scope
- * @param {!AutomationTreeWalker.Restriction} restrictions
- */
-function AutomationTreeWalker(start, scope, restrictions) {
-  /**
-   * Currently highlighted node.
-   *
-   * @private {!chrome.automation.AutomationNode}
-   */
-  this.node_ = start;
-
-  /**
-   * The root of the subtree that the user is navigating through.
-   *
-   * @private {!chrome.automation.AutomationNode}
-   */
-  this.scope_ = scope;
-
-  /**
-   * Function that returns true for a node that is a leaf of the current
-   * subtree.
-   *
-   * @private {!AutomationTreeWalker.Unary}
-   */
-  this.leafPred_ = restrictions.leaf;
-
-  /**
-   * Function that returns true for a node in the current subtree that should
-   * be visited.
-   *
-   * @private {!AutomationTreeWalker.Unary}
-   */
-  this.visitPred_ = restrictions.visit;
-}
-
-/**
- * @typedef {{leaf: AutomationTreeWalker.Unary,
- *            visit: AutomationTreeWalker.Unary}}
- */
-AutomationTreeWalker.Restriction;
-
-/**
- * @typedef {function(!chrome.automation.AutomationNode) : boolean}
- */
-AutomationTreeWalker.Unary;
-
-AutomationTreeWalker.prototype = {
-  /**
-   * Set this.node_ to the next/previous interesting node within the current
-   * scope and return it. If no interesting node is found, return the
-   * first/last interesting node. If |doNext| is true, will search for next
-   * node. Otherwise, will search for previous node.
-   *
-   * @param {boolean} doNext
-   * @return {chrome.automation.AutomationNode}
-   */
-  moveToNode: function(doNext) {
-    let node = this.node_;
-    do {
-      node = doNext ? this.getNextNode_(node) : this.getPreviousNode_(node);
-    } while (node && !this.visitPred_(node));
-    if (node) {
-      this.node_ = node;
-      return node;
-    }
-
-    console.log('Restarting search for node at ' + (doNext ? 'first' : 'last'));
-    node = doNext ? this.scope_ : this.getYoungestDescendant_(this.scope_);
-    while (node && !this.visitPred_(node))
-      node = doNext ? this.getNextNode_(node) : this.getPreviousNode_(node);
-    if (node) {
-      this.node_ = node;
-      return node;
-    }
-
-    console.log('Found no interesting nodes to visit.');
-    return null;
-  },
-
-
-  /**
-   * Given a flat list of nodes in pre-order, get the node that comes after
-   * |node| within the current scope.
-   *
-   * @param {!chrome.automation.AutomationNode} node
-   * @return {!chrome.automation.AutomationNode|undefined}
-   * @private
-   */
-  getNextNode_: function(node) {
-    // Check for child.
-    let child = node.firstChild;
-    if (child && !this.leafPred_(node))
-      return child;
-
-    // Has no children, and if node is root of subtree, don't check siblings
-    // or parent.
-    if (node === this.scope_)
-      return undefined;
-
-    // No child. Check for right-sibling.
-    let sibling = node.nextSibling;
-    if (sibling)
-      return sibling;
-
-    // No right-sibling. Get right-sibling of closest ancestor.
-    let ancestor = node.parent;
-    while (ancestor && ancestor !== this.scope_) {
-      let aunt = ancestor.nextSibling;
-      if (aunt)
-        return aunt;
-      ancestor = ancestor.parent;
-    }
-
-    // No node found after |node|, so return undefined.
-    return undefined;
-  },
-
-  /**
-   * Given a flat list of nodes in pre-order, get the node that comes before
-   * |node| within the current scope.
-   *
-   * @param {!chrome.automation.AutomationNode} node
-   * @return {!chrome.automation.AutomationNode|undefined}
-   * @private
-   */
-  getPreviousNode_: function(node) {
-    // If node is root of subtree, there is no previous node.
-    if (node === this.scope_)
-      return undefined;
-
-    // Check for left-sibling. If a left-sibling exists, return its youngest
-    // descendant if it has one, or otherwise return the sibling.
-    let sibling = node.previousSibling;
-    if (sibling)
-      return this.getYoungestDescendant_(sibling) || sibling;
-
-    // No left-sibling. Return parent if it exists; otherwise return undefined.
-    let parent = node.parent;
-    if (parent)
-      return parent;
-
-    return undefined;
-  },
-
-  /**
-   * Get the youngest descendant of |node|, if it has one, within the current
-   * scope.
-   *
-   * @param {!chrome.automation.AutomationNode} node
-   * @return {!chrome.automation.AutomationNode|undefined}
-   * @private
-   */
-  getYoungestDescendant_: function(node) {
-    if (!node.lastChild || this.leafPred_(node))
-      return undefined;
-
-    while (node.lastChild && !this.leafPred_(node))
-      node = node.lastChild;
-
-    return node;
-  },
-
-  /**
-   * Return the next sibling of |node| if it has one.
-   *
-   * @param {chrome.automation.AutomationNode} node
-   * @return {chrome.automation.AutomationNode}
-   */
-  debugMoveToNext: function(node) {
-    if (!node)
-      return null;
-
-    let next = node.nextSibling;
-    if (next) {
-      return next;
-    } else {
-      console.log('Node is last of siblings');
-      console.log('\n');
-      return null;
-    }
-  },
-
-  /**
-   * Return the previous sibling of |node| if it has one.
-   *
-   * @param {chrome.automation.AutomationNode} node
-   * @return {chrome.automation.AutomationNode}
-   */
-  debugMoveToPrevious: function(node) {
-    if (!node)
-      return null;
-
-    let prev = node.previousSibling;
-    if (prev) {
-      return prev;
-    } else {
-      console.log('Node is first of siblings');
-      console.log('\n');
-      return null;
-    }
-  },
-
-  /**
-   * Return the first child of |node| if it has one.
-   *
-   * @param {chrome.automation.AutomationNode} node
-   * @return {chrome.automation.AutomationNode}
-   */
-  debugMoveToFirstChild: function(node) {
-    if (!node)
-      return null;
-
-    let child = node.firstChild;
-    if (child) {
-      return child;
-    } else {
-      console.log('Node has no children');
-      console.log('\n');
-      return null;
-    }
-  },
-
-  /**
-   * Return the parent of |node| if it has one.
-   *
-   * @param {chrome.automation.AutomationNode} node
-   * @return {chrome.automation.AutomationNode}
-   */
-  debugMoveToParent: function(node) {
-    if (!node)
-      return null;
-
-    let parent = node.parent;
-    if (parent) {
-      return parent;
-    } else {
-      console.log('Node has no parent');
-      console.log('\n');
-      return null;
-    }
-  }
-};

chrome/browser/resources/chromeos/switch_access/tree_walker_unittest.gtestjs

-// Copyright 2017 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-/**
- * Test fixture for tree_walker.js.
- * @constructor
- * @extends {testing.Test}
- */
-function AutomationTreeWalkerUnitTest() {
-  testing.Test.call(this);
-};
-
-AutomationTreeWalkerUnitTest.prototype = {
-  __proto__: testing.Test.prototype,
-
-  /** @override */
-  extraLibraries: [
-    'test_support.js',
-    'tree_walker.js',
-  ],
-
-  /** @override */
-  browsePreload: DUMMY_URL,
-
-  getSampleTree: function() {
-    let loc = {left: 0, top: 0, width: 0, height: 0};
-    // root
-    //   upper1
-    //     middle1
-    //       lower1
-    //         leaf1
-    //         leaf2
-    //         leaf3
-    //       lower2
-    //         leaf4
-    //         leaf5
-    //     middle2
-    //       lower3
-    //         leaf6
-    //         leaf7
-    //   upper2
-    //     leaf8
-    let root = {location: loc, state: {}};
-    let upper1 = {location: loc, state: {}};
-    let upper2 = {location: loc, state: {}};
-    let middle1 = {location: loc, state: {}};
-    let middle2 = {location: loc, state: {}};
-    let lower1 = {location: loc, state: {}};
-    let lower2 = {location: loc, state: {}};
-    let lower3 = {location: loc, state: {}};
-    let leaf1 = {location: loc, state: {}};
-    let leaf2 = {location: loc, state: {}};
-    let leaf3 = {location: loc, state: {}};
-    let leaf4 = {location: loc, state: {}};
-    let leaf5 = {location: loc, state: {}};
-    let leaf6 = {location: loc, state: {}};
-    let leaf7 = {location: loc, state: {}};
-    let leaf8 = {location: loc, state: {}};
-
-    let ts = new TestSupport();
-    ts.setChildren(root, [upper1, upper2]);
-    ts.setChildren(upper1, [middle1, middle2]);
-    ts.setChildren(upper2, [leaf8]);
-    ts.setChildren(middle1, [lower1, lower2]);
-    ts.setChildren(middle2, [lower3]);
-    ts.setChildren(lower1, [leaf1, leaf2, leaf3]);
-    ts.setChildren(lower2, [leaf4, leaf5]);
-    ts.setChildren(lower3, [leaf6, leaf7]);
-
-    return {
-      root: root,
-      upper1: upper1,
-      upper2: upper2,
-      middle1: middle1,
-      middle2: middle2,
-      lower1: lower1,
-      lower2: lower2,
-      lower3: lower3,
-      leaf1: leaf1,
-      leaf2: leaf2,
-      leaf3: leaf3,
-      leaf4: leaf4,
-      leaf5: leaf5,
-      leaf6: leaf6,
-      leaf7: leaf7,
-      leaf8: leaf8
-    };
-  },
-
-  getDefaultRestrictions: function() {
-    return {
-      leaf: function(node) {
-        return false;
-      },
-      visit: function(node) {
-        return node.state.focusable === true;
-      },
-    }
-  },
-
-  getSubtreeRestrictions: function() {
-    return {
-      leaf: function(node) {
-        return node.state.leaf === true;
-      },
-      visit: function(node) {
-        return node.state.focusable === true;
-      },
-    }
-  }
-};
-
-TEST_F('AutomationTreeWalkerUnitTest', 'MoveToNodeWholeTree', function() {
-  let t = this.getSampleTree();
-  let treeWalker = new AutomationTreeWalker(
-      t.root, t.root, this.getDefaultRestrictions());
-
-  t.root.state['focusable'] = true;
-  t.middle1.state['focusable'] = true;
-  t.leaf1.state['focusable'] = true;
-  t.leaf2.state['focusable'] = true;
-  t.leaf5.state['focusable'] = true;
-  t.lower3.state['focusable'] = true;
-  t.leaf6.state['focusable'] = true;
-  t.upper2.state['focusable'] = true;
-  t.leaf8.state['focusable'] = true;
-
-  // Move to next node.
-  assertEquals(t.middle1, treeWalker.moveToNode(true));
-  assertEquals(t.leaf1, treeWalker.moveToNode(true));
-  assertEquals(t.leaf2, treeWalker.moveToNode(true));
-  assertEquals(t.leaf5, treeWalker.moveToNode(true));
-  assertEquals(t.lower3, treeWalker.moveToNode(true));
-  assertEquals(t.leaf6, treeWalker.moveToNode(true));
-  assertEquals(t.upper2, treeWalker.moveToNode(true));
-  assertEquals(t.leaf8, treeWalker.moveToNode(true));
-  assertEquals(t.root, treeWalker.moveToNode(true));
-  assertEquals(t.middle1, treeWalker.moveToNode(true));
-
-  // Move to previous node.
-  assertEquals(t.root, treeWalker.moveToNode(false));
-  assertEquals(t.leaf8, treeWalker.moveToNode(false));
-  assertEquals(t.upper2, treeWalker.moveToNode(false));
-  assertEquals(t.leaf6, treeWalker.moveToNode(false));
-  assertEquals(t.lower3, treeWalker.moveToNode(false));
-  assertEquals(t.leaf5, treeWalker.moveToNode(false));
-  assertEquals(t.leaf2, treeWalker.moveToNode(false));
-  assertEquals(t.leaf1, treeWalker.moveToNode(false));
-  assertEquals(t.middle1, treeWalker.moveToNode(false));
-});
-
-TEST_F('AutomationTreeWalkerUnitTest', 'MoveToNodeInSubtree', function() {
-  let t = this.getSampleTree();
-  let treeWalker = new AutomationTreeWalker(
-      t.upper1, t.upper1, this.getSubtreeRestrictions());
-
-  t.lower2.state['leaf'] = true;
-  t.lower3.state['leaf'] = true;
-
-  t.root.state['focusable'] = true;
-  t.middle1.state['focusable'] = true;
-  t.leaf1.state['focusable'] = true;
-  t.leaf2.state['focusable'] = true;
-  t.leaf5.state['focusable'] = true;
-  t.lower3.state['focusable'] = true;
-  t.leaf6.state['focusable'] = true;
-  t.upper2.state['focusable'] = true;
-  t.leaf8.state['focusable'] = true;
-
-  // Move to next node.
-  assertEquals(t.middle1, treeWalker.moveToNode(true));
-  assertEquals(t.leaf1, treeWalker.moveToNode(true));
-  assertEquals(t.leaf2, treeWalker.moveToNode(true));
-  assertEquals(t.lower3, treeWalker.moveToNode(true));
-  assertEquals(t.middle1, treeWalker.moveToNode(true));
-
-  // Move to previous node.
-  assertEquals(t.lower3, treeWalker.moveToNode(false));
-  assertEquals(t.leaf2, treeWalker.moveToNode(false));
-  assertEquals(t.leaf1, treeWalker.moveToNode(false));
-  assertEquals(t.middle1, treeWalker.moveToNode(false));
-  assertEquals(t.lower3, treeWalker.moveToNode(false));
-});
-
-TEST_F('AutomationTreeWalkerUnitTest', 'GetNextNode', function() {
-  let t = this.getSampleTree();
-  let treeWalker = new AutomationTreeWalker(
-      t.middle1, t.middle1, this.getDefaultRestrictions());
-
-  let order =
-      [t.middle1, t.lower1, t.leaf1, t.leaf2, t.leaf3,
-      t.lower2, t.leaf4, t.leaf5];
-  let node = t.middle1;
-  for (let i = 0; i < order.length; i++) {
-    assertEquals(order[i], node);
-    node = treeWalker.getNextNode_(node);
-  }
-  assertEquals(undefined, node);
-});
-
-TEST_F('AutomationTreeWalkerUnitTest', 'GetPreviousNode', function() {
-  let t = this.getSampleTree();
-  let treeWalker = new AutomationTreeWalker(
-      t.leaf5, t.middle1, this.getDefaultRestrictions());
-
-  let order =
-      [t.leaf5, t.leaf4, t.lower2, t.leaf3, t.leaf2,
-      t.leaf1, t.lower1, t.middle1];
-  let node = t.leaf5;
-  for (let i = 0; i < order.length; i++) {
-    assertEquals(order[i], node);
-    node = treeWalker.getPreviousNode_(node);
-  }
-  assertEquals(undefined, node);
-});
-
-TEST_F('AutomationTreeWalkerUnitTest', 'GetYoungestDescendant', function() {
-  let t = this.getSampleTree();
-  let treeWalker = new AutomationTreeWalker(
-      t.root, t.root, this.getDefaultRestrictions());
-
-  assertEquals(t.leaf8, treeWalker.getYoungestDescendant_(t.root));
-  assertEquals(t.leaf7, treeWalker.getYoungestDescendant_(t.upper1));
-  assertEquals(t.leaf8, treeWalker.getYoungestDescendant_(t.upper2));
-  assertEquals(t.leaf5, treeWalker.getYoungestDescendant_(t.middle1));
-  assertEquals(t.leaf7, treeWalker.getYoungestDescendant_(t.middle2));
-  assertEquals(t.leaf3, treeWalker.getYoungestDescendant_(t.lower1));
-  assertEquals(t.leaf5, treeWalker.getYoungestDescendant_(t.lower2));
-  assertEquals(t.leaf7, treeWalker.getYoungestDescendant_(t.lower3));
-  assertEquals(undefined, treeWalker.getYoungestDescendant_(t.leaf1));
-  assertEquals(undefined, treeWalker.getYoungestDescendant_(t.leaf2));
-  assertEquals(undefined, treeWalker.getYoungestDescendant_(t.leaf3));
-  assertEquals(undefined, treeWalker.getYoungestDescendant_(t.leaf4));
-  assertEquals(undefined, treeWalker.getYoungestDescendant_(t.leaf5));
-  assertEquals(undefined, treeWalker.getYoungestDescendant_(t.leaf6));
-  assertEquals(undefined, treeWalker.getYoungestDescendant_(t.leaf7));
-  assertEquals(undefined, treeWalker.getYoungestDescendant_(t.leaf8));
-});