DO NOT COMMIT DevTools: reintroduce fullViewportUpdate

DevTools: reintroduce fullViewportUpdate

BUG=679815

[luoe, 2017-02-23 23:27:09]

luoe@chromium.org changed reviewers:
+ lushnikov@chromium.org, pfeldman@chromium.org

[luoe, 2017-02-23 23:27:10]

This patch is to reintroduce the fullViewportUpdate that I removed in another
patch that landed https://codereview.chromium.org/2688803002/

I had removed it without realizing the need for a way to trigger wasShown for
all the current messages in the viewport.  This is required for a patch that I
plan to land (https://codereview.chromium.org/2623143002) in which toggling
timestamps setting will call updateMessageList which triggers a full viewport
update, and wasShown()'s will build decorations.

Still need the non-full update invalidate() for things like
scheduleViewportUpdate().  Appending a single new message needs only the partial
update.

ptal

[luoe, 2017-02-24 01:49:40]

Hopefully fullViewportUpdate() is a clearer name that indicates this function
will call willHide for all current messages in viewport and wasShown for all
messages in the viewport, even if they were there before.

[luoe, 2017-03-03 03:55:40]

Description was changed from

==========
DevTools: reintroduce fullViewportUpdate

BUG=679815
==========

to

==========
DevTools: reintroduce fullViewportUpdate

BUG=679815
==========

[luoe, 2017-03-03 03:55:40]

luoe@chromium.org changed reviewers:
- lushnikov@chromium.org, pfeldman@chromium.org