Include scheduling-only threads in tracks

tracing/tracing/ui/tracks/process_track_base.html

Index: tracing/tracing/ui/tracks/process_track_base.html
diff --git a/tracing/tracing/ui/tracks/process_track_base.html b/tracing/tracing/ui/tracks/process_track_base.html
index b56b2cf30029e270679a41392ee3a75f3d5cd538..cce46c86b540355e9e82510d1923f2d1c92e6763 100644
--- a/tracing/tracing/ui/tracks/process_track_base.html
+++ b/tracing/tracing/ui/tracks/process_track_base.html
@@ -16,6 +16,7 @@ found in the LICENSE file.
 <link rel="import" href="/tracing/ui/tracks/frame_track.html">
 <link rel="import" href="/tracing/ui/tracks/object_instance_group_track.html">
 <link rel="import" href="/tracing/ui/tracks/process_summary_track.html">
+<link rel="import" href="/tracing/ui/tracks/sched_group_track.html">
 <link rel="import" href="/tracing/ui/tracks/spacing_track.html">
 <link rel="import" href="/tracing/ui/tracks/thread_track.html">
 
@@ -137,12 +138,6 @@ tr.exportTo('tr.ui.tracks', function() {
       this.didAppendTracks_();
     },
 
-    addEventsToTrackMap: function(eventToTrackMap) {
-      this.tracks_.forEach(function(track) {
-        track.addEventsToTrackMap(eventToTrackMap);
-      });
-    },
-
     willAppendTracks_: function() {
     },
 
@@ -256,14 +251,41 @@ tr.exportTo('tr.ui.tracks', function() {
       threads.sort(tr.model.Thread.compare);
 
       // Create the threads.
+      var schedThreads = [];
+      var hasVisibleThreads = false;
       threads.forEach(function(thread) {
         var track = new tr.ui.tracks.ThreadTrack(this.viewport);
         track.thread = thread;
         if (!track.hasVisibleContent)
           return;
-        Polymer.dom(this).appendChild(track);
-        Polymer.dom(this).appendChild(new SpacingTrack(this.viewport));
+        if (track.hasSlices) {
+          hasVisibleThreads = true;
+          Polymer.dom(this).appendChild(track);
+          Polymer.dom(this).appendChild(new SpacingTrack(this.viewport));
+        } else if (track.hasTimeSlices) {
+          schedThreads.push(thread);
+        }
       }.bind(this));
+
+      if (schedThreads.length > 0) {
+        // If there's only 1 thread with scheduling-only information don't
+        // bother making a group, just display it directly
+        // Similarly if we are a process with only scheduling-only threads
+        // don't bother making a group as the process itself serves
+        // as the collapsable group
+        if (schedThreads.length > 1 && hasVisibleThreads) {

[charliea (OOO until 10-5), 2016/10/26 21:23:37]

I think that we probably want to always add these threads to the SchedGroupTrack
and add the ability to hide the expand/collapse bar for the track. 

My reasoning is that, right now, we only care about showing a simple ThreadTrack
for each of these threads. If, in the future, we have some more custom logic
(like shading an area where we're doing disk I/O in another color for example),
we'd still want the stuff in the else() block of this branch to benefit from
that, whereas now it wouldn't because it wouldn't be piped through the
SchedGroupTrack where it makes sense for that logic to live.

In other words, I think it makes sense to do something like:

var track = new tr.ui.tracks.SchedGroupTrack(this.viewport);
track.threads = schedThreads;
track.collapsible = schedThreads.length > 1 && hasVisibleThreads;

and then handle all of the rest of the logic in sched_group_thread

[John Reck, 2016/10/26 21:55:47]

Done.

+          var track = new tr.ui.tracks.SchedGroupTrack(this.viewport);
+          track.threads = schedThreads;
+          Polymer.dom(this).appendChild(track);
+        } else {
+          schedThreads.forEach(function(thread) {
+            var track = new tr.ui.tracks.ThreadTrack(this.viewport);
+            track.thread = thread;
+            Polymer.dom(this).appendChild(track);
+            Polymer.dom(this).appendChild(new SpacingTrack(this.viewport));
+          }.bind(this));
+        }
+      }
     }
   };