See https://github.com/flutter/flutter/issues/23171

This reverts commit 74662ab6.

This should land after https://github.com/flutter/engine/pull/6442

* Add pragma vm:entry-point

Otherwise, an object may be both null and an instance of EnginieLayer at
the same time in Dart.

Provide a relative, per-image limit to the amount of memory
that's used to cache decoded image frames. Adds an overridable default
that developers can set to control how much memory images are allowed
to use decoded vs undecoded. The cap is set in flutter/flutter#22452.

Note that required frames are always cached regardless of the ratio cap,
because they're currently necessary for the GIF to animate. Previously
cached unessential frames are not cleared in response to the cache
hitting or exceeding the cap.

Addresses #20998 and #14344.

Reverts flutter/engine#6406

We need to fix the SkiaGPUObject issue of the raster cache SkImage before merging this PR.

To make the PR minimal, we currently only share the engine layer when `pushPhysicalShape` (for Fuchsia) or `pushOffset` (for `RepaintBoundary` and `Opacity`) are called. They should be sufficient for our short-term perf goal. In the future, we can incrementally share more engine layers with the framework.

https://github.com/flutter/flutter/issues/21756

Fixes https://github.com/flutter/flutter/issues/19214

So our future pull requests won't be polluted by the white space changes.

This is a reland of #5638. We removed the restoreToCount, made doAntiAlias named, and updated the comments.

This reverts commit a2bf8059.

Reason for revert: need to fix several things including the framework test in order to unblock the engine roll.

TBR: @matthew-carroll 

This would enable us to solve https://github.com/flutter/flutter/issues/18057

See https://github.com/flutter/flutter/issues/9184

Part of fixing https://bugs.chromium.org/p/skia/issues/detail?id=7741

Fixes https://github.com/flutter/flutter/issues/9184

On a Linux host, we were having to convert the type of the bitmap to N32, but we weren't also fixing the channel order to RGBA, so consequently we were getting BGRA when the API was asking for RGBA. This forces the color format to be RGBA when that is what is asked for.

We weren't needing to do conversion on macOS, so macOS was always getting RGBA.

Fixes flutter/flutter#9226

* update docs for getBounds

* Add computeMetrics suggestion

* better explanation

* Support for TwoPointConical gradients

This reverts commit 919e8c21 as it
breaks flutter gradient_test.

Fixes https://github.com/flutter/flutter/issues/12212

Fixes https://github.com/flutter/flutter/issues/11961

Fixes build break introduced in 33aaf6fc.

* Enable sweep gradients

* Use _matrix4IsValid

* Add assert for startAngle < endAngle

* Use radians for startAngle and endAngle

* Update AUTHORS

* Better assert on matrix4IsValid

* add path measure

* fix typo

* getBound and addPathWithMatrix

* Add myself to Authors, add PathOps

* fix linting issues

* update licenses_flutter to add new files

* Use matrix4 instead of matrix3 for consistency/interop

* put pubspec back

* fix bug in getSegment

* fix typo

* Add return value for PathOp

* refactoring from review

* refactoring from review - still TBD on computeMetrics()

* add doc

* lint issue

* fix computeMetrics, add Path.from

* add missing wireup for clone

* change PathMetrics to iterable, fix bug with angle on Tangent

* prefer std::make_unique

* cleanup docs

* add path measure

* fix typo

* getBound and addPathWithMatrix

* Add myself to Authors, add PathOps

* fix linting issues

* update licenses_flutter to add new files

* Use matrix4 instead of matrix3 for consistency/interop

* put pubspec back

* fix bug in getSegment

* fix typo

* Add return value for PathOp

* refactoring from review

* refactoring from review - still TBD on computeMetrics()

* add doc

* lint issue

* fix computeMetrics, add Path.from

* add missing wireup for clone

* change PathMetrics to iterable, fix bug with angle on Tangent

* prefer std::make_unique

* cleanup docs

* fix iterator bug

* remove unnecessary clone for computeMetrics

* fix some doc issues

* fix PathMeasure iterator, extendWithPath, isClosed, and pubspec.lock

* get rid of orElse; use StateException

* StateError, not StateException

* doc improvements and nits

* add unit tests, fix bugs found during testing

* fix two uncommited doc changes

* one more

* change sign of tangent angle, update docs

* update unit tests for inverted angle

* update tangent to include vector

* Doc fixes

* Fix MSVC compilation and unit test

Fixes https://github.com/flutter/flutter/issues/16635

After we write the pixels in the correct format,
the color type of the SkPixmap is still set to
its previous value, so the existing assertion was
failing.

Building image encoding into the engine bloated the
binary size. This change will return raw bytes, and
callers who use this functionality can take on the
dependency on image encoding in their apps (via a
Dart package or a platform plugin).

Fixes https://github.com/flutter/flutter/issues/16537

* Re-land "Support multiple shells in a single process. (#4932)"

This reverts commit 723c7d01.