Timeline: fix reset logic of TracingTimelineModel & co

The way we perform reset (i.e. clear records) was
badly wrong in a couple of places:
 - we generally should only reset the objects that we own,
so TimelineTracingView should have not tried to reset TracingModel;
 - TracingTimelineModel should reset before the record is
started,not after.

BUG=361045

Review URL: https://codereview.chromium.org/326693002

git-svn-id: svn://svn.chromium.org/blink/trunk@175810 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/devtools/front_end/timeline/TimelinePanel.js

@@ -709,6 +709,8 @@ WebInspector.TimelinePanel.prototype = {
 
     _onClearButtonClick: function()
     {
+        if (this._tracingModel)
+            this._tracingModel.reset();
         this._model.reset();
     },
 

third_party/WebKit/Source/devtools/front_end/timeline/TimelineTracingView.js

@@ -55,7 +55,6 @@ WebInspector.TimelineTracingView.prototype = {
 
     reset: function()
     {
-        this._tracingModel.reset();
         this._dataProvider.reset();
         this._mainView.setWindowTimes(0, Infinity);
     },

third_party/WebKit/Source/devtools/front_end/timeline/TracingTimelineModel.js

@@ -101,6 +101,7 @@ WebInspector.TracingTimelineModel.prototype = {
      */
     startRecording: function(captureStacks, captureMemory)
     {
+        this.reset();
         var categories;
         if (WebInspector.experimentsSettings.timelineTracingMode.isEnabled()) {
             categories = WebInspector.TracingTimelineModel.defaultTracingCategoryFilter;
@@ -124,6 +125,7 @@ WebInspector.TracingTimelineModel.prototype = {
      */
     setEventsForTest: function(sessionId, events)
     {
+        this.reset();
         this._didStartRecordingTraceEvents();
         this._tracingModel.setEventsForTest(sessionId, events);
         this._didStopRecordingTraceEvents();
@@ -139,7 +141,6 @@ WebInspector.TracingTimelineModel.prototype = {
 
     _didStartRecordingTraceEvents: function()
     {
-        this.reset();
         this.dispatchEventToListeners(WebInspector.TimelineModel.Events.RecordingStarted);
     },