Changes since last roll:
```
ed303c628 Roll dart sdk again. Previous roll required 23ae4fa098 revert. (#4966)
8cd272733 Revert "Roll dart to 7764e6962e22afcf4b58c4e3cef3147330f3c884. (#4960)" (#4965)
9199b40f2 Revert "Support multiple shells in a single process. (#4932)" (#4964)
6baff4c82 Support multiple shells in a single process. (#4932)
31c5bb427 Roll dart to 7764e6962e22afcf4b58c4e3cef3147330f3c884. (#4960)
c8e4c6984 Avoid copying the contents of large platform message responses (#4947)
5ff527295 Update to use new vulkan GrBackendRenderTarget ctor. (#4962)
0c8993a1a Update to use new vulkan GrBackendRenderTarget ctor (part 2) (#4963)
132ebdda8 Revert "Roll src/third_party/skia/ 9874bf1bc..52e16d984 (135 commits) (#4958)" (#4961)
11882ab9e Roll src/third_party/skia/ 9874bf1bc..52e16d984 (135 commits) (#4958)
```

Add consts

* Update bin/internal/README.md

* Update README.md

See https://github.com/flutter/flutter/issues/12630 and
https://github.com/flutter/flutter/issues/16408

There was a bug in the size calculation for the height of the chip label, where it would force the label to be larger than it wanted to be, causing text to not be vertically centered.

* do not add run spacing if there are no run metrics

Make the full-screen dialog text editable in gallery (#13690)

This fixes https://github.com/dart-lang/sdk/issues/32598.

We are about to begin building gen_snapshot as a multi-arch binary,
which when run as x86_64 will generate arm64 AOT output, and when run as
i386 will generate armv7 AOT output.

Currently, gen_snapshot is an x86_64 binary, so this change is
effectively preventative in nature, and is a no-op with the current
snapshotter.

* Update text_style_test

* Update template .gitignore rules

* Remove old packages rule

* Remove IDE folders from gitignore templates

* Prefer ios.tmpl/.gitignore

* Update text_form_field.dart

* Update text_form_field_test.dart

* Update text_form_field_test.dart

* Update text_form_field_test.dart

* Bump mockito to 3.0.0-alpha+3

* Type annotation

Switch to the new Matrix4.tryInvert method to avoid throwing and catching (#15771) exceptions while performing hit testing.

Fixes https://github.com/flutter/flutter/issues/16332

* always schedule first frame when creating ticker, regardless of phase or frame

* Remove explicit child nodes

* Remove semantics on no-op menu buttons

* Add a dummy action to the overflow bar

Includes:
* Add armv7 support to create_ios_framework script (#4942)
* Roll Dart to version 09e1766e6caa537e1271fbce04ebcbf8212b6569 (#4941)

This renames the chip's border attribute to 'shape' so that it is consistent with the other places where we supply a ShapeBorder.

This is a breaking change, but a very small one: the border attribute was introduced only a few months ago, and is not widely used.

* Roll engine to version be070599a30413bd203f2d77d2179220c5569c08
(includes a roll of dart to version 3e6b8717fedce5cc28a21616f4591683c211f752

Fixes https://github.com/flutter/flutter/issues/16200