Always retarget blur events to the root of the focused node

Given events a_1, .., a_n that come in in the same update,
where a_i is a blur and a_j is focus (i < j).

Then, a_i's update params focused id will point to a_j's node.

As a result, we never actually fire a_j properly since it was seen as "already" focused.

TEST=navigate context menus in files app.
BUG=668775

Review-Url: https://codereview.chromium.org/2575233002
Cr-Commit-Position: refs/heads/master@{#439116}

chrome/renderer/resources/extensions/automation_custom_bindings.js

@@ -93,6 +93,14 @@ automationUtil.updateFocusedNode = function() {
   automationUtil.focusedNode = automationUtil.getFocus();
 };
 
+/**
+ * Updates the focus on blur.
+ */
+automationUtil.updateFocusedNodeOnBlur = function() {
+  var focus = automationUtil.getFocus();
+  automationUtil.focusedNode = focus ? focus.root : null;
+};
+
 automation.registerCustomHook(function(bindingsAPI) {
   var apiFunctions = bindingsAPI.apiFunctions;
 
@@ -287,7 +295,7 @@ automationInternal.onAccessibilityEvent.addListener(function(eventParams) {
     // events but otherwise not handle blur events specially.
     var node = privates(targetTree).impl.get(eventParams.targetID);
     if (node == node.root)
-      isFocusEvent = true;
+      automationUtil.updateFocusedNodeOnBlur();
   } else if (eventParams.eventType == schema.EventType.mediaStartedPlaying ||
       eventParams.eventType == schema.EventType.mediaStoppedPlaying) {
     // These events are global to the tree.