Roll engine 2b94311a7764..4f888d66250e (10 commits) (#55749)

https://github.com/flutter/engine/compare/2b94311a7764...4f888d66250e

git log 2b94311a7764..4f888d66250e --first-parent --oneline
2020-04-25 nurhan@google.com Change the repo fetch script used in integration tests (flutter/engine#17943)
2020-04-24 skia-flutter-autoroll@skia.org Roll src/third_party/skia 1e21d14f2b8b..c12aad9485a9 (20 commits) (flutter/engine#17942)
2020-04-24 skia-flutter-autoroll@skia.org Roll src/third_party/dart a69cb6d700f5..216e3df4526c (16 commits) (flutter/engine#17945)
2020-04-24 xster@google.com Fix accessibility focus loss when first focusing on text field (flutter/engine#17803)
2020-04-24 skia-flutter-autoroll@skia.org Roll fuchsia/sdk/core/linux-amd64 from _dAFU... to G4HpJ... (flutter/engine#17938)
2020-04-24 mouad.debbar@gmail.com [web] Fix exception when getting boxes for rich text range (flutter/engine#17933)
2020-04-24 ferhat@gmail.com [web] Batch systemFontChange messages (flutter/engine#17885)
2020-04-24 skia-flutter-autoroll@skia.org Roll fuchsia/sdk/core/linux-amd64 from kpECk... to _dAFU... (flutter/engine#17929)
2020-04-24 skia-flutter-autoroll@skia.org Roll src/third_party/skia b965ff597315..1e21d14f2b8b (25 commits) (flutter/engine#17928)
2020-04-24 skia-flutter-autoroll@skia.org Roll src/third_party/dart 94178e920ee8..a69cb6d700f5 (22 commits) (flutter/engine#17926)

bin/internal/engine.version

-2b94311a776460e9cad83808ade901d51aedf34f
+4bcfae82c7c18460c1558cea52c993ebe4439a03