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Consider two views: A and its child view B.

The "Views::Layout" trace event for B is currently emitted when A calls
B's Layout as part of A's Layout. This is less intuitive than calling it
in B's Layout, but is better because it can capture an event for a B
which doesn't call through to the base class Layout implementation in
its Layout.

Unfortunately, this still leaves many gaps:
1) Layout managers
2) Views whose *parents* don't call the base class implementation
3) Layouts triggered by bounds changes
4) Probably some more I can't think of right now.

This change adds extra trace events to address #3 from the list above.

Bug: 850128, 835983
Change-Id: I135ac0e8b2c6b9e277dce6da06e9d0aeae7dfbd1
Reviewed-on: https://chromium-review.googlesource.com/1112466
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Reviewed-by: Robert Liao <robliao@chromium.org>
Reviewed-by: Trent Apted <tapted@chromium.org>
Cr-Commit-Position: refs/heads/master@{#570065}