Now that keyboard height is modelled as a (bottom) view inset, migrate
scaffold bottom resizing to use view insets instead of bottom padding,
which, after an engine roll, will only be used for safe areas.

Until the aforementioned engine roll, the keyboard height is still
included in both bottom padding and view insets. As such
resizeToAvoidBottomPadding still drives bottom padding removal until
that roll lands.

Renames _ScaffoldLayout.bottomPadding to bottomViewInset

This patch contains no framework changes.

This change adjusts a test bottom navigation bar height to be greater
than the media bottom padding.

This change is pre-factoring to clarify diffs in an upcoming change that
will expose bottom padding to the bottom navigation bar in order to
allow it to visually adapt its appearance in the presence of bottom
padding such as thatexposed for the iPhone X home screen indicator.
Since the bottom padding was previously greater than the height of the
bottom navigation bar, the height of insideBottomNavigation bar was
driven to 0 when padding is exposed.

Scaffold bottom padding now applies the maximum of window
viewInsets.bottom (typically used for iOS safe areas) and padding.bottom
(typically used for keyboard height).

Adds `Scaffold#endDrawer` property to supply a second drawer to a Scaffold.

* Drop invisible SemanticsNodes from tree

A node is invisible if it is outside of the bounds of the screen and if it is not merged into its (partially) visible parent.

Also in this PR: only set `wasAffectedByClip` to true if the nodes has actually been clipped.

* Fix other failing tests

* renaming

* review feedback

* more doc

* SafeArea

* AnimatedSafeArea

* AppBar test

* Apply feedback

* upgrade to linter-0.1.35

* re-enable lint prefer_const_constructors

* address review comments

Fixes #11369

* Exclude modal barrier from semantics on Android

* Add tests

Adds a widgets that blocks all semantics of widgets below it in paint order within the same container (#10425)

backgroundColor -> color
backgroundImage -> image
BackgroundImage -> DecorationImage

* more widget const constructors

* prefer const constructors

* address review comments

* make @immutable const

* fix build

* Scaffold appBar is-a PreferredSizeWidget, etc

* Updated

* Updated per review feedback

* Manually fix every use of Point.x and Point.y

Some of these were moved to dx/dy, but not all.

* Manually convert uses of the old gradient API

* Remove old reference to Point.

* Mechanical changes

I applied the following at the root of the Flutter repository:

git ls-files -z | xargs -0 sed -i 's/\bPoint[.]origin\b/Offset.zero/g'
git ls-files -z | xargs -0 sed -i 's/\bPoint[.]lerp\b/Offset.lerp/g'
git ls-files -z | xargs -0 sed -i 's/\bnew Point\b/new Offset/g'
git ls-files -z | xargs -0 sed -i 's/\bconst Point\b/const Offset/g'
git ls-files -z | xargs -0 sed -i 's/\bstatic Point /static Offset /g'
git ls-files -z | xargs -0 sed -i 's/\bfinal Point /final Offset /g'
git ls-files -z | xargs -0 sed -i 's/^\( *\)Point /\1Offset /g'
git ls-files -z | xargs -0 sed -i 's/ui[.]Point\b/ui.Offset/g'
git ls-files -z | xargs -0 sed -i 's/(Point\b/(Offset/g'
git ls-files -z | xargs -0 sed -i 's/\([[{,]\) Point\b/\1 Offset/g'
git ls-files -z | xargs -0 sed -i 's/@required Point\b/@required Offset/g'
git ls-files -z | xargs -0 sed -i 's/<Point>/<Offset>/g'
git ls-files -z | xargs -0 sed -i 's/[.]toOffset()//g'
git ls-files -z | xargs -0 sed -i 's/[.]toPoint()//g'
git ls-files -z | xargs -0 sed -i 's/\bshow Point, /show /g'
git ls-files -z | xargs -0 sed -i 's/\bshow Point;/show Offset;/g'

* Mechanical changes - dartdocs

I applied the following at the root of the Flutter repository:

git ls-files -z | xargs -0 sed -i 's/\ba \[Point\]/an [Offset]/g'
git ls-files -z | xargs -0 sed -i 's/\[Point\]/[Offset]/g'

* Further improvements and a test

* Fix minor errors from rebasing...

* Roll engine

* Wiring fullscreen dialog

* Make fullscreen dialog use the new API. Add tests

* Review notes

* Move field back up

* final

Aggressively apply the const lint.

The new name follows the pattern of the name suggesting which layout
protocol the parent expects the child to speak.

Fixes #8664

* prefer const constructors

* fix double throw

This ensures that both timer/microtask queues are cleared out rather
than assuming that all work is completed in a specified amount of time.

Fixes #8413

It's common to just want a simple colored box. Simple thing should be simple,
so this patch adds a convenience argument to Continer for creating a box
decoration that is just a color.

Fixes #5555

Rename all the "2" classes related to scrolling to remove the "2". Now that the
old scrolling code is gone, we don't need to use the suffix.

All the clients have migrated to Scrollable2.

Move the back button and drawer opening logic into the app bar.

Move the tap-status-bar-to-scroll-to-top logic to using
ScrollControllers. Provide a PrimaryScrollController and a `primary`
flag on scroll views.

Make it possible to track when a route becomes or stops being poppable.

This patch removes unnecessary uses of scrollableKey from tests.
Scrollable2 will likely use a different mechanism for identifying
itself, so we want to focus on the uses of scrollableKey that will need
to be addressed in the new implementation.

This widget is a replacement for ScrollableViewport that uses the new
Scrollable2 machinery. The widget is not based on Slivers but does use the new
scroll behavior classes.

...now that we have generic methods, their types need to be specified too.

People get confused by the tight constraints.

Fixes #616

The spec forbids persistent bottom sheets from overlapping the app bar. There
are also some fancy scroll-linked effects that we're supposed to do with
persistent bottom sheets, but those will need to wait for another patch.

Fixes #5143