This reverts commit 5b3dc525.

This reverts commit 4518a72f.

* migrate part of painting to nullsafety

* address review comments

* address review comment

* increase the number of shards for web tests

* update comments

* 8a0e30b36 Roll Dart SDK from 2d98d25e71c3 to c59cdee365b9 (1 revision) (flutter/engine#20200)

* 0519052c8 Roll Dart SDK from c59cdee365b9 to ad9c73cb3270 (1 revision) (flutter/engine#20201)

* fc5b7779d Roll Skia from 7225788b9070 to 8e77631a80f0 (8 revisions) (flutter/engine#20184)

* cb8dfdb29 Roll Skia from 8e77631a80f0 to a6df9da28963 (17 revisions) (flutter/engine#20202)

* ea811fc77 Roll Dart SDK from ad9c73cb3270 to 0f0e04ec3afa (3 revisions) (flutter/engine#20204)

* 02d71d60e Use a single mask view to clip iOS platform view (flutter/engine#20050)

Updates all the dependencies used in the most basic test and flutter_test isolates.

f86b83010 Roll Dart SDK from 365525432a70 to 2d98d25e71c3 (1 revision) (flutter/engine#20198) (#62770)

* 7f5d044f3 Wait before switching surfaces (flutter/engine#20100)

* 5513273d0 Reland: Avoid a copy in EncodeImage (flutter/engine#20003)

* 1efdd9538 Roll Dart SDK from bd528bfbd69d to ea6bde577d1c (19 revisions) (flutter/engine#20172)

* 3b0e697db Roll Skia from 8cc118dce813 to c3794dd52778 (27 revisions) (flutter/engine#20173)

* cb1a37401 Roll Fuchsia Mac SDK from T2xc0OuiK... to i0zTcQ8Qb... (flutter/engine#20175)

* ed36b1aa2 Roll Skia from c3794dd52778 to 2d01ed94605a (10 revisions) (flutter/engine#20179)

* fcc1eaf8f Fix iOS Keyboard stuck as UIKeyboardTypeNamePhonePad (flutter/engine#20181)

* 9c6837c2b Roll Skia from 2d01ed94605a to 7225788b9070 (6 revisions) (flutter/engine#20183)

* 13e993ed1 Fix Typos (flutter/engine#19691)

* 98cfd1db7 Move platform specific information to `PlatformConfiguration` class (flutter/engine#19652)

* 22fb58b77 update nullability of drawAtlas methods and flesh out docs (flutter/engine#20176)

* bcc43dfb6 Roll Dart SDK from ea6bde577d1c to 033a81d924b9 (23 revisions) (flutter/engine#20186)

* cb4bb93d9 [web] increase number of shards. sync engine web tests same as flutter repo (flutter/engine#20164)

* d986b8d60 Enable linting in several files (flutter/engine#20134)

* 7dd092dd3 Enable more linting (flutter/engine#20187)

* 3cc86ac13 Roll Dart SDK from 033a81d924b9 to ad5bcf16f1c8 (9 revisions) (flutter/engine#20191)

* 5ca8a2a0e Roll Dart SDK from ad5bcf16f1c8 to d169af6f7d8f (1 revision) (flutter/engine#20192)

* 4de0c048d Roll Dart SDK from d169af6f7d8f to 7e6c55e3aaf5 (1 revision) (flutter/engine#20196)

* 908fe012d Fix navigation message relay. (flutter/engine#20193)

* f1b3b6981 Roll Dart SDK from 7e6c55e3aaf5 to 365525432a70 (2 revisions) (flutter/engine#20197)

* 8fbdd3f1b Fix parameter names

* 083282e33 Fix Implments typo

The flutter tool already has an attach integration test: https://github.com/flutter/flutter/blob/master/packages/flutter_tools/test/integration.shard/flutter_attach_test.dart

The devicelab test frequently fails with difficult to debug issues and is not worth the maintenance cost.

NNBD migration for services