Remove global variables from compile.dart and devices.dart (except for dds which needs more changes).

#47161

Fixes https://github.com/flutter/flutter/issues/67343

* adds titleSpacing in AppBarTheme
Co-authored-by: Shi-Hao Hong <shihaohong@google.com>

Reland "Add CompositedTransformFollower.{followerAnchor, leaderAnchor} for custom anchoring (#64930)" (#65871) (#65884)

Just converting some test files to NNBD

* enable null_check_on_nullable_type_parameter and tighten_type_of_initializing_formals

* fix CI

Work around the glibc bug that causes rare Chrome crashes

Migrate Material framework tests to null safety.

When setting the TextSelection in a TextEditingController, preserve the
composing range so long as the new selection is:

  * a collapsed selection; in other words, a cursor rather than a
    selection with an extent. A selection with an extent is not
    permitted when composing.
  * within the composing region. Moving the cursor outside the composing
    region ends composing mode.

When using physical keyboards for input with an IME, users expect to be
able to navigate using the cursor within the composing region with the
arrow keys in order to edit text in the composing range.

As an example, a user might erroneously enter the composing text
にほんごにゅうろく in kana, then hit the left arrow, followed by
backspace in order to delete the ろ, then input りょ in order to
generate the correct composing text にほんごにゅうりょく, before then
hitting the conversion key to convert to the kanji text 日本語入力 and
commit.

This reverts commit 76cbc462.

This reverts commit 2e419ff7.

This reverts commit d4112424.

Errors that happen in user-defined callbacks (like onChanged) will now make it to the console.

There have been some more additional reports of a missing 'package:characters' import after upgrading flutter, as well as problems with detecting the correct language version. This has me concerned that our pub caching logic is incorrect. Instead of the tool attempting to guess when pub should be run, always delegate to pub.