Define a minimum delay time for processing live regions on the same node.

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

 // Copyright 2015 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.
 
 /**
  * @fileoverview Implements support for live regions in ChromeVox Next.
  */
 
 goog.provide('LiveRegions');
 
@@ skipping 36 matching lines @@
 
 /**
  * Live region events received in fewer than this many milliseconds will
  * queue, otherwise they'll be output with a category flush.
  * @type {number}
  * @const
  */
 LiveRegions.LIVE_REGION_QUEUE_TIME_MS = 500;
 
 /**
+ * Live region events received on the same node in fewer than this many
+ * milliseconds will be dropped to avoid a stream of constant chatter.
+ * @type {number}
+ * @const
+ */
+LiveRegions.LIVE_REGION_MIN_SAME_NODE_MS = 20;
+
+/**
  * Whether live regions from background tabs should be announced or not.
  * @type {boolean}
  * @private
  */
 LiveRegions.announceLiveRegionsFromBackgroundTabs_ = true;
 
 LiveRegions.prototype = {
   /**
    * Called when the automation tree is changed.
    * @param {TreeChange} treeChange
@@ skipping 61 matching lines @@
 
     output.withSpeechCategory(cvox.TtsCategory.LIVE);
 
     if (!output.hasSpeech)
       return;
 
     // Enqueue live region updates that were received at approximately
     // the same time, otherwise flush previous live region updates.
     var currentTime = new Date();
     var queueTime = LiveRegions.LIVE_REGION_QUEUE_TIME_MS;
-    if (currentTime - this.lastLiveRegionTime_ > queueTime) {
-      this.liveRegionNodeSet_ = new WeakSet();
+    var delta = currentTime - this.lastLiveRegionTime_;
+    if (delta > queueTime) {
       output.withQueueMode(cvox.QueueMode.CATEGORY_FLUSH);
       this.lastLiveRegionTime_ = currentTime;
     } else {
       output.withQueueMode(cvox.QueueMode.QUEUE);
     }
 
+    if (delta > LiveRegions.LIVE_REGION_MIN_SAME_NODE_MS)
+      this.liveRegionNodeSet_ = new WeakSet();
+
     var parent = node;
     while (parent) {
       if (this.liveRegionNodeSet_.has(parent))
         return;
       parent = parent.parent;
     }
 
     this.liveRegionNodeSet_.add(node);
     output.go();
   },
 };
 
 });  // goog.scope