**tl;dr:** A `RenderObject` can only be an effective semantics boundary if it actually owned a `SemanticsNode` in the previous tree generation.

When using the `BlockSemantics` widget it is possible to introduce `RenderObject`s that are configured to be a semantics boundary, but because their semantics are blocked by `BlockSemantics` they will not (immediately) end up owning a `SemanticsNode`. When now a descendant of such a node-less semantics boundary marks itself as needing a semantics update we walk up the tree until we find the closest semantics boundary (which is our node-less `RenderObject`). We now incorrectly assume that this semantics boundary has a valid `SemanticsNode` and only regenerate the semantics subtree below this node. However, because the identified semantics boundary doesn't actually own a valid `SemanticsNode` asserts are throwing (e.g. `Child with id xx is invisible and should not be added to tree.`).

To fix this problem, we can just abort the walk if we reach a semantics boundary without a semantics node because (for now) we know that the semantics information of this branch will not make it into the final semantics tree.
If the semantics block is ever removed, the current algorithm re-generates the semantics for the entire branch and the semantics will be up-to-date then despite the abort. I've added a test to verify this to make sure it continues to work even when we change the algorithm.

Fixes https://github.com/flutter/flutter/issues/13326.
/cc @gavindoughtie FYI

This attempts to apply some of what we learnt from UX studies, namely
that people wonder how to add multiple children to widget that take
one child.

This is a collection of fixes I've run into recently.

Hopefully this will fix the performance regression in https://github.com/flutter/flutter/pull/13680 but with an easier way to flip the switch.

Small code changes as part of moving the framework SDK forward to a 2.0 dev version.

This cleans up lerp, lerpFrom, lerpTo, and scale methods, and their
documentation.

Fixes https://github.com/flutter/flutter/issues/12377.

This reverts commit dbd3eb67.

Commit above fixed initial problem with frontend_server on Windows, but caused another more explicit problem with gen_snapshot down the line.

* localize a11y tab labels in the TabBar

* break import cycle

* test boilerplate

* fix German translation

* more test boilerplate fixes

* other accounts a11y; show accounts button a11y

* layout with bigger tap areas; all semantics

* internationalize UserAccountsDrawerHeader a11y labels

* better Russian translation

* break import cycle

* address comments

This reverts commit 765191e7.
because the updated packages cause a gradle build problem.

This adds our self-compiled copy of the MinGit executable (built from the flutter/git repo) to the archive when building an archive for Windows.

I also tweaked the internal API for prepare_package.dart so that there's a single entry point to build an archive.

Fixes #12877 by reverting #9472

Adds .vscode/ to the .gitignore rules generated on flutter create.

* support increase and decrease SemanticsActions in time picker

* test roll over

* selected ListTile is selected

* review comment

* analyzer fix

* Gen localization classes intead of a big map

* tighten up the newlines so that std output matches file output

* restore locale sorting

* Change async stubbing to use thenAnswer.

Mockito now prohibits calling thenReturn with Futures and Streams. dart-lang/mockito#79

* Update all Mockito deps to 3.0.0.

* Revert "Update all Mockito deps to 3.0.0."

This reverts commit e8ab9d37c33d3d7fe384abde64ea5b4d72623c75.

I did not correctly update the mockito dep, and there's no easy way to update to 3.0 alpha right now.

* Change thenAnswer((_) => to thenAnswer((invocation) =>

* Add Invocation type to thenAnswer lambdas

Prevent header from thinking it can wrap and then overflowing.

Fix default footer string which lost its colon (localized values are fine).

Make the "rows per page" drop-down include at least one value even when the table lacks many items. (Previously it would assert if your table was too short.)

Make the footer scrollable.

Fix some todos and improve some debug output.

Tests for much of the above.

* IconButton is a button, semantically

* fix datepicker test

Applies horizontal safe area insets to the Pesto demo in the Gallery.
This is to support the iPhone X sensor housing notch and other similarly
creative display features when in landscape orientation.

A modern version of 7Zip (7za.exe) is now installed on the bots, this makes use of that.

This replaces the use of ideviceinfo (whose output was then filtered for
device IDs) with an invocation idevice_id -l, which returns the list
directly, one per line.