* Set text direction in semantics along with Directionality

* update tests for the extra SemanticsNode

CompilerOutput values should never be mutated. Also includes minor
formatting change to the compile() method signature in line with the
style guide.

Minor housekeeping while I'm touching other bits of nearby code.

Pre-factoring for addition of AOT snapshotting unit tests, which emit a
different set of expected outputs.

Wraps the compile function in a class injected via the global context,
which makes it easier to mock in unit tests -- specifically tests for
AOT snapshotting, which already require pretty significant amounts of
mock inputs.

* [fuchsia] Pass a dummy command to the ssh tunnel setup

* Address analyzer lint

* Update fuchsia_remote_debug_protocol

Changes include:

flutter/engine@ec61147 replace nextNodeId/previousNodeId with hitTestPosition
flutter/engine@2970c09 Use the default microtask scheduler on all isolates except the UI isolate
flutter/engine@96af3b2 ios: remove geometric order; it will be supplied by framework
flutter/engine@3b84a47 Apply unaddressed comments in pull/5062
flutter/engine@29816a6 Roll src/third_party/skia/ 3d0e8507f..5209d7fce (14 commits)
flutter/engine@4691a0b Import intrusively ref counted shared pointers into FML.

Fixes https://github.com/flutter/flutter/issues/16496

Renames buildSnapshot to build buildScriptSnapshot in preparation for
AOT snapshot tests.

New a11y traversal:

- sort direct sibling SemanticsNodes only
- use new sorting algorithm
- implement RTL
- test semantics in traversal order by default
- add AppBar traversal test
- breaking: remove nextNodeId/previousNodeId from the framework
- breaking: remove DebugSemanticsDumpOrder.geometricOrder

When passing a Color object with same R/G/B code ( e.g. [new Color.fromRGBO(100, 100, 100, 1.0)] ) to HSVColor.fromColor(Color color) , the hue in return will be NaN .

As pointed out in the bug, the issue is fixed by just clamping sizeFactor.value.

Fixes #16247 

This adds a toImage function to RenderRepaintBoundary that returns an uncompressed raw image of the RenderRepaintBoundary and its children. A device pixel ratio different from the physical ratio may be specified for the captured image. A value of 1.0 will give an image in logical pixels.

This addresses #16593 by removing the unneeded assert in the setter for constrainedAxis. Null was meant to be allowed there.

This replaces #16599 and fixes #16593, reported by @maksimr

This replaces the existing manual invocation with the GenSnapshot class,
which allows for better configuration and testability.

Package projects were erroneously being treated as apps

This avoids notifying the coverage collector that we
completed the test when in fact we timed out, which in
turn avoids a downstream exception caused by the fact
that coverage collector assumes it has a valid observatory
port by which it can gather coverage data.

Fixes https://github.com/flutter/flutter/issues/16839

This contains the following commit:

flutter/engine@cb3376c Support different encodings in Image.toByteData() (#16635)

* add the full path to a flutter command

* remove an unused import

* review comments

We were trying to only catch WebSocketException, but in fact
SocketException can be thrown as well.

This engine roll contains the following commits:

* flutter/engine@09d05a389: Prepare and run child isolates on a VM managed (i.e. no UI) task runner.
* flutter/engine@adee35142: Throw an error or return null if FlutterView.getBitmap fails

Fixes #13655