MD Bookmarks: Scroll and select items that are added to the main list

chrome/browser/resources/md_bookmarks/timer_proxy.js

Index: chrome/browser/resources/md_bookmarks/timer_proxy.js
diff --git a/chrome/browser/resources/md_bookmarks/timer_proxy.js b/chrome/browser/resources/md_bookmarks/timer_proxy.js
index de96c7fdb4ec7aa2b5bfe9c2329ccaff095de13f..88ae8762f58fdd07aa2f094162042e30f8f0c274 100644
--- a/chrome/browser/resources/md_bookmarks/timer_proxy.js
+++ b/chrome/browser/resources/md_bookmarks/timer_proxy.js
@@ -27,7 +27,51 @@ cr.define('bookmarks', function() {
     },
   };
 
+  /**
+   * A timer which will fire on the next task after the last time it is reset.

[calamity, 2017/07/26 05:36:06]

nit: This isn't strictly true. It gets added to the task list each time, so the
last reset can have a bunch of tasks between itself and the actual callback
firing.

How about:

A one-shot debouncer which fires the given callback after a delay. The delay can
be refreshed by calling resetTimer. Resetting with no delay moves the callback
to the end of the task queue.

[tsergeant, 2017/07/26 06:34:07]

Done.

+   * @param {function()} callback
+   * @constructor
+   */
+  function Debouncer(callback) {

[tsergeant, 2017/07/25 00:13:00]

I'm happy enough with this for now, but one unanswered question is how we make
this testable, both in terms of getting a 'TestDebouncer' instance, and how we
inject a TestTimerProxy into it.

[calamity, 2017/07/26 05:36:06]

Acknowledged.

+    this.callback_ = callback;
+    this.timerProxy_ = new TimerProxy();
+    this.timer_ = null;
+    this.boundTimerCallback_ = this.timerCallback_.bind(this);
+    this.isDone_ = false;
+    this.promiseResolver_ = new PromiseResolver();

[calamity, 2017/07/26 05:36:06]

nit: Couple of types?

[tsergeant, 2017/07/26 06:34:07]

Done.

+  }
+
+  Debouncer.prototype = {
+    resetTimer: function() {

[calamity, 2017/07/26 05:36:06]

nit: resetTimeout perhaps? This will be given a delay param in my auto expander
patch. (Or just do it now to align with the class comment I suggested)

[tsergeant, 2017/07/26 06:34:07]

Done.

+      if (this.timer_)
+        this.timerProxy_.clearTimeout(this.timer_);
+      this.timer_ = this.timerProxy_.setTimeout(this.boundTimerCallback_);
+    },
+
+    /**
+     * @return {boolean} True if the Debouncer has finished processing.
+     */
+    done: function() {
+      return this.isDone_;
+    },
+
+    /**
+     * @return {Promise} Promise which resolves immediately after the callback.
+     */
+    get promise() {
+      return this.promiseResolver_.promise;
+    },
+
+    /** @private */
+    timerCallback_: function() {
+      this.isDone_ = true;
+      this.callback_.call();
+      this.promiseResolver_.resolve();
+    },
+  };
+
   return {
+    Debouncer: Debouncer,
     TimerProxy: TimerProxy,
   };
 });