Update 1.17 engine hash to Dart 2.8.4 (#18783)

* Update 1.17 engine hash to Dart 2.8.4

* update license file for Dart

* Upgrade the meta package version for compatibility with petitparser-3.0.4 (#18700)

Co-authored-by: Jason Simmons <jason-simmons@users.noreply.github.com>
diff --git a/DEPS b/DEPS
index 74c00b7..2654f9c 100644
--- a/DEPS
+++ b/DEPS
@@ -34,7 +34,7 @@
   # Dart is: https://github.com/dart-lang/sdk/blob/master/DEPS.
   # You can use //tools/dart/create_updated_flutter_deps.py to produce
   # updated revision list of existing dependencies.
-  'dart_revision': '9a618e5661665b8d687a28e6b1ec25e9177ec2d7',
+  'dart_revision': 'caebd6700d5ece73b5566b33ff1daecb91dac500',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py
diff --git a/ci/licenses_golden/licenses_third_party b/ci/licenses_golden/licenses_third_party
index cde342f..79448e4 100644
--- a/ci/licenses_golden/licenses_third_party
+++ b/ci/licenses_golden/licenses_third_party
@@ -1,4 +1,4 @@
-Signature: 9b730253ef8e88721ca9e72eddab75a8
+Signature: 2c5216c3466ba2ed3a7c2d4ca382a157
 
 UNUSED LICENSES:
 
diff --git a/lib/web_ui/pubspec.yaml b/lib/web_ui/pubspec.yaml
index 7574325..ea720ae 100644
--- a/lib/web_ui/pubspec.yaml
+++ b/lib/web_ui/pubspec.yaml
@@ -5,7 +5,7 @@
   sdk: ">=2.2.2 <3.0.0"
 
 dependencies:
-  meta: 1.1.7
+  meta: 1.1.8
 
 dev_dependencies:
   http: 0.12.0+4