Fixes https://github.com/dart-lang/sdk/issues/61597
* Remove the old caching mechanism for the old way of sourcing files.
* Remove BlazeMockPackages._addFiles, and rename _addFiles2 to
_addFiles.
A few trailing fixing included:
* Flex.new has a required direction parameter.
* TextOverflow comes from
'package:flutter/src/painting/text_painter.dart'.
* A few stray imports needed to resolve types.
* DiagnosticableTree.debugDescribeChildren is marked external so
that subclasses need not implement it themselves.
* In sort_child_properties_last, RawMaterialButton is in the material
library.
Change-Id: I092bad587ea39bceb7af0951eada3963b1eb48bb
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/473542
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Samuel Rawlins <srawlins@google.com>
Sam Rawlins
1c87e41254