DevTools: introduce WebInspector.Throttler

Source/devtools/front_end/common/Throttler.js

Index: Source/devtools/front_end/common/Throttler.js
diff --git a/Source/devtools/front_end/common/Throttler.js b/Source/devtools/front_end/common/Throttler.js
new file mode 100644
index 0000000000000000000000000000000000000000..b5596633a81cc5b69c0fa856dd100b53cb4e1969
--- /dev/null
+++ b/Source/devtools/front_end/common/Throttler.js
@@ -0,0 +1,61 @@
+// Copyright 2014 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.
+
+/**
+ * @constructor
+ * @param {number} timeout
+ */
+WebInspector.Throttler = function(timeout)
+{
+    this._timeout = timeout;
+    this._isRunningProcess = false;
+    this._somethingScheduled = false;
+    this._asSoonAsPossible = false;
+}
+
+WebInspector.Throttler.prototype = {
+    _processCompleted: function()
+    {
+        this._isRunningProcess = false;
+        if (this._somethingScheduled)
+            this._innerSchedule();
+    },
+
+    _onTimeout: function()
+    {
+        this._processTimeout = null;
+        this._somethingScheduled = false;
+        this._isRunningProcess = true;
+        this._process(this._processCompleted.bind(this));
+    },
+
+    /**
+     * @param {function(!WebInspector.Throttler.FinishCallback)} process
+     * @param {boolean=} asSoonAsPossible
+     */
+    schedule: function(process, asSoonAsPossible)
+    {
+        this._somethingScheduled = true;
+        // Deliberately skip previous process.
+        this._process = process;
+        this._asSoonAsPossible = this._asSoonAsPossible || !!asSoonAsPossible;

[dgozman, 2014/06/09 12:03:33]

I think, the general usage of throttler is: immediately issue first operation,
postpone next ones for a certain timeout.
To achieve this, I should pass |asSoonAsPossible=true| to the first call, which
is inconvenient. And how do you I even find out it's the first call?

[lushnikov, 2014/06/09 13:07:26]

Agreed. Will fix this in next CL

+
+        if (this._isRunningProcess)
+            return;
+
+        this._innerSchedule();
+    },
+
+    _innerSchedule: function()
+    {
+        if (this._processTimeout)

[dgozman, 2014/06/09 07:01:51]

How can this be non-null?

[lushnikov, 2014/06/09 09:45:53]

It is set to null as the timeout fires. @see _onTimeout function

+            return;
+        var timeout = this._asSoonAsPossible ? 0 : this._timeout;
+        this._asSoonAsPossible = false;
+        this._processTimeout = setTimeout(this._onTimeout.bind(this), timeout);
+    }
+}
+
+/** @typedef {function()} */

[dgozman, 2014/06/09 07:01:51]

function(function) ?

[lushnikov, 2014/06/09 09:45:53]

Nope, the typedef here is correct.

[dgozman, 2014/06/09 12:03:33]

My bad.

+WebInspector.Throttler.FinishCallback;