DevTools: Support JS frames save/load for tracing timeline.

Source/devtools/front_end/timeline/TracingModel.js

Index: Source/devtools/front_end/timeline/TracingModel.js
diff --git a/Source/devtools/front_end/timeline/TracingModel.js b/Source/devtools/front_end/timeline/TracingModel.js
index 2e8d98a88071a6d62e931b410b994a43efae4e5d..5af2e87d31ddeaebb0802c1fc8f1d14472b73332 100644
--- a/Source/devtools/front_end/timeline/TracingModel.js
+++ b/Source/devtools/front_end/timeline/TracingModel.js
@@ -552,6 +552,7 @@ WebInspector.TracingModel.Process = function(id)
 {
     WebInspector.TracingModel.NamedObject.call(this);
     this._setName("Process " + id);
+    this._id = id;
     this._threads = {};
     this._objects = {};
     /** @type {!Array.<!WebInspector.TracingManager.EventPayload>} */
@@ -562,6 +563,14 @@ WebInspector.TracingModel.Process = function(id)
 
 WebInspector.TracingModel.Process.prototype = {
     /**
+     * @return {number}
+     */
+    id: function()
+    {
+        return this._id;
+    },
+
+    /**
      * @param {number} id
      * @return {!WebInspector.TracingModel.Thread}
      */