In 77af1e5e, dart:vmservice_sky was
renamed to dart:vmservice_io.

* Add support for NDK discovery and add --prefer-shared-library option

We would like to be able to use native tools (e.g. simpleperf, gdb) with
precompiled flutter apps.  The native tools work much better with *.so
files instead of the custom formats the Dart VM uses by default.

The reason for using blobs / instruction snapshots is that we do not
want to force flutter users to install the Android NDK.

This CL adds a `--prefer-shared-library` flag to e.g. `flutter build
apk` which will use the NDK compiler (if available) to turn the
precompiled app assembly file to an `*.so` file.  If the NDK compiler is
not available it will default to the default behavior.

* Rebase, add test for NDK detection, augment flutter.gradle with @Input for flag

* Use InMemoryFileSystem for test

* Remove unused import

* Address some analyzer warnings

gen_snapshot loads all packages from single app kernel file.

Add hidden options --extra-front-end-options and --extra-gen-snapshot-options to flutter tool (#12219)

This CL introduces 2 hidden options to 'flutter build aot' and 'flutter run' for passing arbitrary arguments to front-end server and to gen_snapshot tool when building and running flutter app in --profile or --release modes.

The ability to pass arbitrary options simplifies various experiments, as it removes the need to change defaults and rebuild flutter engine for every tested configuration.

Checksum validation is intended only as a performance improvement.
Checksum de-serialization errors (typically framework version mismatch) are
expected on framework updates and shouldn't be user-visible except for
informational purposes when --verbose is set.

Adds the app entrypoint as a key in the checksum file.

This change eliminates the assumption that checksummed files change when
the main entrypoint changes. In the case where there are two
entrypoints, a.dart and b.dart and a.dart imports b.dart and b.dart
imports a.dart, building the app with entrypoint a.dart followed by a
build of the app with entrypoint b.dart would result in the same
files list and checksums, but should invalidate the build.

This adds --preview-dart-2 flag that enables use of Dart 2.0 Frontend in Flutter tools.

Extract a Snapshotter class that can be shared between FLX snapshotting,
AOT snapshotting, and assembly AOT snapshotting. Allows for better
testability of snapshotting logic.

* Extracts script snapshotting used in FLX build.
* Adds tests for snapshot checksumming, build invalidation/skipping.

Remaining work: disentangle + extract AOT snapshotting and Assembly AOT
snapshotting logic from build_aot.dart.

This change re-introduces skipping AOT snapshot builds if input sources
and outputs have not changed since the last snapshot build, assuming a
build for the same platform in the same build mode.

This reverts commit 3d5afb5a.
It includes the following changes relative to the original:
  1. Include the entrypoint source in the checksums
  2. include the build mode in the checksums
  3. include the target platform in the checksums

This reverts commit 1705bf3c.

* Revert "Fix a typo in the saved certificate error message (#11640)"

This reverts commit bfda885a.

* Revert "Rollback patch that broke microbenchmarks (#11616)"

This reverts commit 70fe6f4c.

* Revert "Extract snapshotting logic to Snapshotter class (#11591)"

This reverts commit 309a2d78.

* Revert "Minor whitespace formatting fix (#11590)"

This reverts commit bf69c3c6.

* Revert "Avoid rebuilding snapshots if no change to source (#11551)"

This reverts commit 74835db5.

This change re-introduces skipping snapshot builds if input sources (and
outputs) have not changed since the last snapshot build, with a bugfix
to include the entry-point source in the checksum used to check whether
rebuild can be skipped. This ensures that the following sequence
invalidates the cached build, resulting in two snapshot builds:

  flutter build ios lib/foo.dart
  flutter build ios lib/bar.dart

This reverts commit 3d5afb5a.

* Revert "Support space- and backslash-escaped dependencies (#11090)"

This reverts commit e6bafd0b.

* Revert "Skip AOT snapshot build if inputs are unchanged (#11084)"

This reverts commit b5e522e2.

Previously, the snapshot file was recomputed on every build. We now
record checksums for all snapshot inputs (which are catalogued in the
snapshot dependencies file output alongside the snapshot) and only
rebuild if the checksum for any input file (or the previous output file) has
changed.

`adb` can sometimes hang, which will in turn hang the Dart isolate if
we're using `Process.runSync()`. This changes many of the `Device` methods
to return `Future<T>` in order to allow them to use the async process
methods. A future change will add timeouts to the associated calls so
that we can properly alert the user to the hung `adb` process.

This is work towards #7102, #9567

**THIS IS A BREAKING CHANGE.** See below for migration steps for
existing projects.

Previously, Flutter app code was built as a raw dylib on iOS.  Dynamic
libraries outside of a framework bundle are not supported on iOS, except
for the system Swift libraries provided by Xcode.

See:
https://developer.apple.com/library/content/technotes/tn2435/_index.html#//apple_ref/doc/uid/DTS40017543-CH1-TROUBLESHOOTING_BUNDLE_ERRORS-EMBEDDED__DYLIB_FILES

* Migrates Xcode build from app.dylib to App.framework
* Migrates flutter create template
* Migrates example projects

Migration steps for existing projects
=====================================

The following steps should be taken from the root of your Flutter
project:

1. Edit `ios/.gitignore`: add `/Flutter/App.framework` on a new line.
2. In the Xcode project navigator, remove `app.dylib` from the Flutter
   folder. Delete this file from the `ios/Flutter` directory in your project.
3. Run a build to generate `ios/Flutter/App.framework`. From the command
   line, run `flutter build ios`. If you have not configured app signing
   in Xcode, an alternative method is to open the simulator, then run
   `flutter run -d iP`.
4. In the Xcode project navigator, select the `Runner` project. In the
   project settings that are displayed in the main view, ensure that the
   `Runner` target is selected. You can verify this by exposing the
   sidebar using the [| ] icon in the upper-left corner of the main
   view.
5. Select the *General* tab in the project settings. Under the
   *Embedded Binaries* section, click '+' to add `App.framework`. In the
   sheet that drops down, click the *Add Other...* button. Navigate to
   the `ios/Flutter` directory and select `App.framework`. Click *Open*.
   In the sheet that drops down, select *Create folder references*, then
   click *Finish*.
6. In the project settings, verify that `App.framework` has been added to the
   *Embedded Binaries* and *Linked Frameworks and Libraries* lists.
7. In the Xcode project navigator, drag `App.framework` under the
   Flutter folder.
8. In the Xcode project navigator, select `Flutter` then from the
   *File* menu, select *Add Files to "Runner"...*. Navigate to the
   `ios/Flutter` directory, select `AppFrameworkInfo.plist` and click
   the *Add* button.
9. From the command line, in your project directory, run
   `flutter build clean`, then `flutter run`.

At this point your project should be fully migrated.

Changed the default build output directory in the new project template
to build/, instead of android/build/ and android/app/build/.

Updated tools to ask the Gradle scripts what the build directory is,
since this is configurable in the build scripts, and we need to know
where the build output actually is.

Silenced output from 'flutter build aot' when invoked from Gradle, since
the output was confusing in this case.

Fixes #8723
Fixes #8656
Fixes #8138

* Use snapshot's .d file as source inputs in Gradle build.

If we don't yet have a .d file (first build), fall back to using the
.dart files in the current directory. This enables us to detect changes
in dependent source files (Flutter framework, packages outside the
source directory, etc.), and re-generate the snapshots as needed.

Unfortunately, Gradle requires knowing the source files before executing
the task, and can't update them after building, so Gradle considers the
second build to be out-of-date (because it has more input files than the
first build). Sub-sequent builds have the correct dependency
information, and will be skipped if the source files haven't changed.

Also added a dependency on gen_snapshot. The snapshot ABI isn't stable,
so we need to re-generate the snapshots when we roll the Dart SDK
dependency.

Fixes #8315
Fixes #8687
Fixes #8607

* Enable Hot Reload on Windows (backed by gen_snapshot)

\o/

Two caveats:
* Hot Reload on Windows is slower than on other platforms because gen_snapshot is slower then sky_snapshot
* We currently cannot hot reload projects with spaces in the path

* enable tests

Artifacts are now located in a central place.
This will enable us to downlaod artifacts when we need them (instead of
downloading them all upfront).
This also makes replacing sky_snapshot with gen_snapshot easier.

Update stack_trace_test.dart for changes to the naming of async body functions.

See https://github.com/flutter/flutter/issues/7579

* improve the logger ui a bit for elapsed times

* invert param

* update daemon.dart