* Ensure that the _childElements map is properly traversed as a sparse list and not inflated with garbage collected children.

* Add tests to ensure Lists/Tabs with KeepAlive children can make large jumps, don't lose children (including after rebuild).

* added shortcuts and delete functionality

* added first test

*  afew chnages

* a few changes

* hope this works

* small change

* small changes

* fixed nits

* final changes:

* fixed initializing formals

* update comment

* minor change:

* added line

* final changes

* random change

* changed function to void

* one more

* removed line

* dis betta work

* final change

* actual final chnge

Fixes #21250

https://github.com/flutter/engine/compare/269880b761a5...d52e5cca03fb

git log 269880b761a5..d52e5cca03fb --no-merges --oneline
d52e5cca0 Roll src/third_party/skia cd9d074578e0..a2bc1ca21bbc (8 commits) (flutter/engine#6211)


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https://github.com/flutter/engine/compare/1770f8854835...269880b761a5

git log 1770f8854835..269880b761a5 --no-merges --oneline
269880b76 Roll src/third_party/skia 40c7c64572bc..cd9d074578e0 (6 commits) (flutter/engine#6210)


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* [Material] Corrects default switch color.

* [Switch] Making black32 a local const.

* [Switch] Tests for default colors.

* [Switch] Correcting number for being over 255.

https://github.com/flutter/engine/compare/5c1a826eec4d...1770f8854835

git log 5c1a826eec4d..1770f8854835 --no-merges --oneline
1770f8854 Remove mention of Garnet/Topaz from license (flutter/engine#6209)


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https://github.com/flutter/engine/compare/e27a2e955bc3...5c1a826eec4d

git log e27a2e955bc3..5c1a826eec4d --no-merges --oneline
5c1a826ee Roll src/third_party/skia a3dc329d1db1..40c7c64572bc (1 commits) (flutter/engine#6208)
bf3c22419 Roll src/third_party/skia 2810c856dfa2..a3dc329d1db1 (1 commits) (flutter/engine#6206)
b9523318c Allow embedders to specify a custom GL proc address resolver. (flutter/engine#6204)
bf96dbed3 Revert "Some cleanups enabled by removing support for Dart. (#5621)" (flutter/engine#6205)
335811560 Roll src/third_party/skia 094b3eaf479c..2810c856dfa2 (6 commits) (flutter/engine#6203)
4c2448d15 Some cleanups enabled by removing support for Dart. (flutter/engine#5621)


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* Update fuchsia-tester so it takes map of kernel test files

* Set mainDart correctly. Cleanup nits.

* update gitignore template to mirror

* Add a newline to end of doc

* remove Android/ and iOS/ subfolder gitignores

Fixes https://github.com/flutter/flutter/issues/21215

* Fix Dropdown where icon not set to end of button

* Expand DropdownButton based on isExpanded flag

* Add dropdown golden tests

Fixes #13135, #16606

Now that Dart 1 support has been eliminated, generator should always be
populated to a kernel compiler instance.

Also moves the constructor to the top of the class, and orders final
fields before non-final fields, as dictated by the style guide.

This tickled a bug in KernelCompiler.compile() where the fingerprinter
doesn't include the outputFilePath in its list of dependencies. As such,
if the output .dill file is missing or corrupted, the fingerprint still
matches and re-compile is skipped, even though it shouldn't be. I'll fix
that in a followup, then look at how this triggered that issue. My
hypothesis is that that it's due to the aot kernel compile and bundle
kernel compile have separate output directories for the .dill files
(build/ vs build/aot) but the same output directory for the associated
depfiles (due to this patch).

This reverts commit 43a106e9.

This reverts commit 6e7f3e6f.

* added shortcuts and delete functionality

* added first test

*  afew chnages

* a few changes

* hope this works

* small change

* small changes

* fixed nits

* final changes:

* fixed initializing formals

* update comment

* minor change:

* added line

* final changes

The --snapshot argument was only necessary in Dart 1. The --depfile
argument was only used in Dart 2 mode to pass to the kernel compiler,
but was inconsistent with the 'build aot' command, where the depfile was
always set to build/kernel_compile.d.

This patch updates 'build bundle' to emit the depfile to a location
consistent with the 'build aot' command; since it's not intended to be
user-configurable and flutter.gradle hardcodes the location to
build/kernel_compile.d either way, this patch also eliminates the
ability to configure the filename altogether.

Revert "Revert "Enable taking screenshots of arbitrary RenderObjects from a running a… (#20637)" (#21395)" (#21448)

This reverts commit 5b5a5b82.

* lint unnecessary_new on samples

* fix tests

* Added music_note icon

This reverts commit 343b5703.

Reverting because the assert introduced in framework.dart(inheritFromElement) is breaking certain Mulligan pages. @hixie suspects it might be due to global keys.

* Update goldens for flutter/engine#6184

* Roll engine to 9b297b3b51228...

* Add build test for Flutter codelabs

* Fix indentation in build test script

* Correct filename for the codelabs build test run by travis

* Change if statement to elif

* Replace echo statements with set -x

* Add BSD-style license

* Add codelabs build test to Cirrus

* Remove codelabs_build_test from Travis.

* Remove codelabs_build_test from travis_script.sh

* Update documentation for codelabs_build_test.sh

* Update readme for build test

* Add link to open a new issue to MDC-Flutter

* Add phrase to address "if you think you really need to break this test, please escalate this"