DevTools: add extension API to contribute trace events to timeline

third_party/WebKit/Source/devtools/front_end/extensions/ExtensionTraceProvider.js

-/**
- * @unrestricted
- */
+// Copyright 2016 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.
+
 Extensions.ExtensionTraceProvider = class {
   /**
    * @param {string} extensionOrigin
    * @param {string} id
    * @param {string} categoryName
    * @param {string} categoryTooltip
    */
   constructor(extensionOrigin, id, categoryName, categoryTooltip) {
     this._extensionOrigin = extensionOrigin;
     this._id = id;
     this._categoryName = categoryName;
     this._categoryTooltip = categoryTooltip;
   }
-  start() {
-    Extensions.extensionServer.startTraceRecording(this._id);
+
+  /**
+   * @param {!Extensions.TracingSession} session
+   */
+  start(session) {
+    var sessionId = String(++Extensions.ExtensionTraceProvider._lastSessionId);
+    Extensions.extensionServer.startTraceRecording(this._id, sessionId, session);
   }
 
   stop() {
     Extensions.extensionServer.stopTraceRecording(this._id);
   }
+
+  /**
+   * @return {string}
+   */
+  shortDisplayName() {
+    return this._categoryName;
+  }
+
+  /**
+   * @return {string}
+   */
+  longDisplayName() {
+    return this._categoryTooltip;
+  }
+
+  /**
+   * @return {string}
+   */
+  persistentIdentifier() {
+    return `${this._extensionOrigin}/${this._categoryName}`;
+  }
 };
+
+Extensions.ExtensionTraceProvider._lastSessionId = 0;
+
+/**
+ * @interface
+ */
+Extensions.TracingSession = function() {}
+
+Extensions.TracingSession.prototype = {
+  /**
+   * @param {string} url
+   * @param {number} timeOffsetMicroseconds
+   */
+  complete: function(url, timeOffsetMicroseconds) { }
+}