This reverts commit cdc631c4.

When the EncodableValue implementation changed, the old version was
temporarily kept behind an #ifdef to allow temporarily using the old
version, so that the roll would not be blocked. All known existing
clients have migrated, so the legacy version is no longer necessary.

* [gn] Adds a flag to turn off git hash versioning

Without this flag, it is excessively tedious to build Dart SDK
for local testing on Fuchsia, since Fuchsia runner will reject
a Dart SDK without a matching version.

* [gn] Add flag --no-dart-version-git-info

This flag suppresses the SDK stamping by git hash, which allows
deploying self-built Dart SDK.  Without this flag, it is impossible
to build and deploy a development Dart SDK on Fuchsia.

GLFW Error callback useful to clarify reasons of 'glfwInit()' failure.

On some platforms/desktop environments may be really strange failure reasons, like (in my case): "Linux: Failed to initialize inotify: Too many open files", so descriptive error messages helps to solve problem.

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/fuchsia-mac-sdk-flutter-engine
Please CC zra@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/master/autoroll/README.md

* isCloneOf for Image

* Update docs, add missing impl

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/fuchsia-linux-sdk-flutter-engine
Please CC zra@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/master/autoroll/README.md

Fixes https://github.com/flutter/flutter/issues/65619

* web: make a few variables non-null

Allows for reference counting of images before disposal.

This will allow multiple callers to hold a reference to an image and dispose of their reference without disposing the underlying image until all handles have been disposed.

This will be used by the framework to help resolve some of the kludge I was trying to introduce in flutter/flutter#64582

Tweaked the label here a little for style ("apps", not "application" -- plural and shorter); and "launching" rather than "re-launching"?

for Android and iOS and remove offset from scenario_app test for iOS and Android.