Applies left, right, and bottom media padding (e.g. iOS safe area
insets) around ButtonBar in the material scaffold
persistentFooterButtons.

* Reject requests for hot reload if a hot reload is already in progress.

Fixes #14184

* Implement TODO, verifying further hot reloads complete sucessfully.

* Fix year on new file.

* Add missing type annotations to fix lints

* Add run_machine_concurrent_hot_reload to manifest for CI

* Reformat document

... but undo things that cause lints (like single-line ifs)

* Extract std stream transformations

* Make inProgressHotReload private

* Disallow all types of reload while hot reload in progress

* Simplify code handling in-progress hot reloads

This is done to keep in place the workaround we have for rectangular material
where PhysicalModel skips the saveLayer call.

While the documentation for MaterialType.canvas described it as
an infinite shape. The implementation has been clipping it to the
bounding rectangle for a while. And it is already used in the wild as a
rectangular piece. So we just update the documentation to match that.

This reverts commit d9ef7df9.

Applies horizontal and bottom safe area insets to the Shrine demo in the
Gallery. Top insets are not applied due to the presence of the
omnipresent sliver app bar. Specifically, this ensures that the grid
cards are inset inside the iPhone X notch in horizontal mode, and that
the bottom of the grid is positioned above the iOS home indicator.

This changes the publishing of archives so that it happens on the chrome_infra bots when they build a packaged branch instead of as part of the dev_roll process.

It uses the tagged version in the branch, and leaves the git repo that it clones checked out on the branch and hash used to build the package.

It updates metadata located at gs://flutter_infra/releases/releases_.json (where is one of macos, linux, or windows) once published, since it would be complex to do the proper locking to keep them all in one shared .json file safely.

A separate [change to the chrome_infra bots](https://chromium-review.googlesource.com/c/chromium/tools/build/+/902823) was made to instruct them to build packaged for the dev, beta, and release branches (but not master anymore).

As a convenience, this adds a set of minimum padding to apply. The
greater of the minimum padding and the media padding is applied to each
edge.

A SafeArea-like widget that applies a SliverPadding instead of a
Padding.

This adds an API for defining the semantic node traversal order.

It adds a sortOrder argument to the Semantics widget, which is a class that can define a list of sort keys to sort on. The keys are sorted globally so that an order that doesn't have to do with the current widget hierarchy may be defined.

It also adds a shortcut sortKey argument to the Semantics widget that simply sets the sortOrder to just contain that key.

The platform side (flutter/engine#4540) gets an additional member in the SemanticsData object that is an integer describing where in the overall order each semantics node belongs. There is an associated engine-side change that takes this integer and uses it to order widgets for the platform's accessibility services.

* Keep the intermediate APK signed the same way before going to the play store

* Don't run on PRs

Discovered during an a11y review of the gallery.

Previously, the iOS ApplicationPackage subclasses did not mark the
bundleID constructor parameter as @required. This is passed up to the
ApplicationPackage constructor as the id parameter which is already
marked @required and is asserted to be non-null.

When diagnosing a failed Xcode build, if neither the development team
(for automatic provisioning) nor the provisioning profile (for manual
provisioning) is set, display the appropriate error message. Previously,
this method would not output the appropriate error message if a
only a development team was set.

- Add override of border color of CupertinoNavigationBar
- Add background color to CupertinoPageScaffold

* Fix scrolling of multiple SliverLists and SliverGrids

* Update sliver_fixed_extent_list.dart

* Update sliver_grid.dart

* iOS works

* Works on Android

* Take in commit number in iOS also. Get rid of image upload for Android. It's just a waste of bandwidth

* Tweak to fix on Travis

* Widget Inspector support for tracking Widget creation locations.

* Add arguments to dartdoc.dart for Dartdoc's grinder and travis

* Fix bug in filter

Fixes https://github.com/flutter/flutter/issues/14393