commit 9d95a254125279c7b235fe9b1a2decb2ce7e5233
author Deepanjan Roy <dproy@google.com> Thu Aug 09 10:10:19 2018 -0400
committer Deepanjan Roy <dproy@google.com> Thu Aug 09 10:10:19 2018 -0400
tree df339dc7c23530a80fc866b71c13d8a42bfee3ac
parent 7f71d0ea7ed3746af20714846f5ecb86a8871269

Refactor Scrolling and Tracks using Panels

In this CL:
* We introduce the interface Panel, which only two methods: renderCanvas
  and updateDom.
* Tracks are internally reimplemented as Panels. Track extension API
  remains unchanged (except they now get timeScale and
  visibleWindowMs through a global.)
* Introduce LightRedrawer, which schedules rafs for high frequency
  drawing. All canvas drawing now happens through LightRedrawer,
  although m.redraw still remains in most places until we change
  overview timeline to work with LightRedrawer.
* Lift out state used by canvas redrawing to global FrontendLocalState
  object, since attributes do not propagate through the mithril tree
  if m.redraw is not called.
* Scrolling architecture is simplified. CanvasController, Scrollable
  Container, and CanvasWrapper are all gone, replaced with the single
  ScrollingPanelContainer.

What's not in this CL:
* We don't have a non-scrolling panel container. We can factor out the
  common code between scrolling and non-scrolling container and do that
  in a seperate CL.
* We don't have any additional panels other than tracks.

Known issues:
* The trace doesn't draw after loading until you pan/zoom for the first
  time. We will need to initialize the time scale and visibleWindowMs
  properly after a trace load.


Change-Id: I924be19e10e160f710dae920bfa1927e66ec8be9