Time-aligned panels should track mouse position in the timeline-axis

[hotsphink]

edit from Greg: This is an older issue, but see the comment below for the work that needs to happen here.

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When I mouse around, a vertical bar is shown in the upper views. I would like that on the Timeline view as well.

[gregtatum]

I'm editing your title a bit to reflect that we should annotate the time better. The timeline view should have vertical markers showing the timing information, and then should also include information about the current time.

[clarkbw]

@hotsphink With the addition of the tooltips in the flame chart is this still needed?

[hotsphink]

Something is still needed. With the tooltips, I'm no longer sure it's a good idea to have a vertical bar when you're mousing over the timeline view; seems like it might be too noisy. But the underlying request is to better correlate your ephemeral position (the one from a mouseover) between the timeline view and the... why can't I ever remember what you call the upper views? So, let me modify the request:

When mousing over the upper pane, I would like a vertical bar to show the matching position in the timeline. When mousing over the timeline (flame graph), I would like the vertical bar to appear in the upper pane. Note that I do not expect these vertical bars to line up, eg if you have a portion of the upper pane selected so that the timeline is only showing that selection. But that's kind of the point -- there are two regions displaying time-based information. When my mouse is in one, I want to see the corresponding position displayed somehow in the other one. The vertical bar is the most obvious (to me) way to do it, given its current use when your mouse is within the upper pane.

[gregtatum]

Changing this to polish, as it's a relatively simple request.

[julienw]

The work here would be to put the "mouse time position" in the redux state, and draw vertical lines out of this state in our various time-based panels (top timeline, stack chart, marker chart, network chart).