Upgrade the analyzer package to version 0.39.15 for Dart 2.10 support (#20024)

ci/build.sh

@@ -18,5 +18,4 @@ flutter/ci/licenses.sh
 cd flutter/web_sdk
 pub get
 cd ..
-# TODO(jsimmons): reenable this when the analyzer has been updated for Dart 2.10
-# dart web_sdk/test/api_conform_test.dart
+dart web_sdk/test/api_conform_test.dart

lib/web_ui/pubspec.yaml

@@ -8,7 +8,7 @@ dependencies:
   meta: 1.1.8
 
 dev_dependencies:
-  analyzer: 0.39.10
+  analyzer: 0.39.15
   http: 0.12.1
   image: 2.1.13
   js: 0.6.1+1
@@ -16,6 +16,7 @@ dev_dependencies:
   path: 1.7.0
   test: 1.14.3
   quiver: 2.1.3
+  build_resolvers: 1.3.10
   build_runner: 1.10.0
   build_test: 1.0.0
   build_web_compilers: 2.11.0

web_sdk/pubspec.yaml

@@ -2,5 +2,5 @@ name: web_sdk_tests
 author: Flutter Authors <flutter-dev@googlegroups.com>
 
 dev_dependencies:
-  analyzer: ^0.39.10
+  analyzer: ^0.39.15
   test: any