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..398e03fd2c7db285c9c8cddf6c86e8d3e9e60b2f
--- /dev/null
+++ b/Source/devtools/front_end/common/Throttler.js
@@ -0,0 +1,88 @@
+// 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._asSoonAsPossible = false;
+    /** @type {?function(!WebInspector.Throttler.FinishCallback)} */
+    this._process = null;
+}
+
+WebInspector.Throttler.prototype = {
+    _processCompleted: function()
+    {
+        this._isRunningProcess = false;
+        if (this._process)
+            this._innerSchedule(false);
+    },
+
+    _onTimeout: function()
+    {
+        delete this._processTimeout;
+        this._asSoonAsPossible = false;
+        this._isRunningProcess = true;
+
+        // Process might issue synchronous calls to this throttler.
+        var process = this._process;
+        this._process = null;
+        process(this._processCompleted.bind(this));
+    },
+
+    /**
+     * @param {function(!WebInspector.Throttler.FinishCallback)} process
+     * @param {boolean=} asSoonAsPossible
+     */
+    schedule: function(process, asSoonAsPossible)
+    {
+        // Deliberately skip previous process.
+        this._process = process;
+        var force = !!asSoonAsPossible && !this._asSoonAsPossible;
+        this._asSoonAsPossible = this._asSoonAsPossible || !!asSoonAsPossible;
+
+        this._innerSchedule(force);
+    },
+
+    /**
+     * @param {boolean} force
+     */
+    _innerSchedule: function(force)
+    {
+        if (this._isRunningProcess)
+            return;
+        if (this._processTimeout && !force)
+            return;
+        if (this._processTimeout)
+            this._clearTimeout(this._processTimeout);
+
+        var timeout = this._asSoonAsPossible ? 0 : this._timeout;
+        this._processTimeout = this._setTimeout(this._onTimeout.bind(this), timeout);
+    },
+
+    /**
+     *  @param {number} timeoutId
+     */
+    _clearTimeout: function(timeoutId)
+    {
+        clearTimeout(timeoutId);
+    },
+
+    /**
+     * @param {function()} operation
+     * @param {number} timeout
+     * @return {number}
+     */
+    _setTimeout: function(operation, timeout)
+    {
+        return setTimeout(operation, timeout);
+    }
+}
+
+/** @typedef {function()} */
+WebInspector.Throttler.FinishCallback;