Introduced a new highlighter option that makes each region <path> element in the highlighter only
cover the actual area of the corresponding region, excluding the area of nested regions.
This is useful when used with the existing showOnly region because it lets users see exactly where
a given region is.
This patch makes the layout-view use this new option, so that when users hover over the various
regions in the layout-view, only the corresponding regions are highlighted.
We used to rely on the TabActor a lot in
/toolkit/devtools/server/actors/highlighter.
This object was being passed around to various highlighter classes, helper
classes and functions.
It was a useful way to get access to the window the highlighters are shown,
listen to DOM events in that window, and also listen to tabActor's will-navigate
events.
Using this object isn't the best idea because it assumes the debugger server is
started and attached to a tab, which makes re-using highlighters outside of this
context impossible (or harder).
Plus we wanted to get rid of the tabActor reference in gcli command contexts.
This change introduces a HighlighterEnvironment that fulfills the requirements
above without relying on a tabActor.
It needs to be initialized either with a tabActor, when we have one (when using
the highlighter from the inspector panel), or with a window (which is what gcli
commands will use).
This change also fixes the highlight command and the rulers command (which
didn't work well with e10s either).
This prevents the WalkerActor from failing at handling various requests when
those requests are about DeaedNodes. Indeed, the async nature of the devtools
protocol means that the client could be asking for information about a node that
doesn't exist anymore because it was part of a page that was navigated away from.
The WalkerActor should know how to deal with such cases, so the patch adds a
number of early returns and a new test for them.
This helps avoiding the inspector-panel from going blank in some edge cases.
LayoutHelpers.getAdjustedBoxQuads now returns all quads that el.getBoxQuads returns.
The BoxModelHighlighter calculates an outer rect based on these to draw the guides.
And if the element has more than 1 quad (inline element that spans line breaks), then all quads are
highlighted.
Also all related tests were modified and a couple of new tests were added.
