This registers a test font manager that maps all fonts to the Ahem font

Fixes https://github.com/flutter/flutter/issues/12513

They help the analysis service identify packages and are now mandatory on Fuchsia.

ClearDartWrapper will delete this SceneBuilder, causing deletion of the
LayerBuilder

This was used by AndroidSurfaceSoftware but is now obsolete

Make sure we await for the file writing to complete before reporting that compilation is done. (#4210)

* Fix RunBundleAndSource to run from kernel.

This is needed to accommodate restarting(rather than reload) of Flutter app from kernel.

* Fix formatting

Move layer tree construction into flow::LayerBuilder so alternate builders can be plugged in. (#4197)

* Roll dart to 87538ffd7eca3405d13e46dcf3a20dcdcde9761e

* Update license hash

* Revert "Revert "Change kernel platform generation dependency name (#4189)" (#4192)"

This reverts commit a91e7b0c.

* Remove bad change that broke the build

* Remove comma

This reverts commit fa46eca4.

This reverts commit 83224fb6.

* Change kernel platform generation dependency name

* Include vmservice which is needed by gen_snapshot for Flutter release build

...if the environment is already setup

* Add reset method to reset incremental compiler.

This is needed to support Flutter app restart request.

* Indent constructor calls

Revert "Revert "Roll dart to pick up change where platform.dill was removed (#4180)" (#4185)" (#4186)

This reverts commit a89f4669.

Doing the synchronized roll of Dart into engine as well as into Fuchsia
to prevent Fuchsia breakage.

This reverts commit 37f571ee.

* Roll dart to pick up change where platform.dill was removed

* Fix flutter patch sdk generation

* Update license hash. No changes to license text.

* Roll dart to pick up a fix for zero-rebuild problem

* Update license hash

This changes Paragraph::Layout to iterate line-by-line through the text.
For each line, Layout scans for word boundaries and adds extra space between
words if the line is justified.

Added it to a few targets.

This reverts commit d43d3534.

Clear regression to the flutter_gallery_ios__transition_perf benchmarks:
  * average_frame_build_time_millis: 1.4x
  * missed_frame_build_budget_count: 1.2x

No regression seen for other iOS benchmarks (e.g. scrolling).

* Switch from FlutterFastaTarget to FlutterTarget as FlutterFastaTarget was removed.

* Change to new SkFontMgr API

These changes clarify ownership rules and work today. They will be
necessary once SK_SUPPORT_LEGACY_FONTMGR_API goes away.

* Fix spacing

* Formatting

When checking whether render buffer size has changed, apply the device
scale factor used to convert points to pixels to ensure we're not
needlessly re-allocating render buffer storage.

Adds trace + debug log to make this easier to detect in future.

Originally introduced in 2d530dae, but
rolled back in 0a6e415b to test whether
it was responsible for regressions to
flutter_gallery_ios__transition_perf benchmarks:
  * average_frame_build_time_millis
  * missed_frame_build_budget_count

This reverts commit 0d2f0cb6.

Attempting to roll into the framework causes analysis errors with
mock classes implementing HTTP-related classes previously in dart:io:
[error] Classes can only implement other classes. (packages/flutter_tools/test/base/net_test.dart, line 94, col 41)
[error] Classes can only implement other classes. (packages/flutter_tools/test/base/net_test.dart, line 62, col 33)
[error] Classes can only implement other classes. (packages/flutter_tools/test/base/net_test.dart, line 78, col 40)
[error] Classes can only implement other classes. (packages/flutter_tools/test/src/context.dart, line 249, col 46)

and dartdoc failures:
dartdoc:stdout: [error] Target of URI doesn't exist: 'dart:_http'. at /home/travis/build/flutter/flutter/bin/cache/pkg/sky_engine/lib/io/io.dart, line 206.