Add Intro to flutter_gpu (#2265)

## Pre-launch Checklist

- [x] I read the [Effective Dart: Style] _recently_, and have followed
its advice.
- [x] I signed the [CLA].
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-devrel
channel on [Discord].

<!-- Links -->
[Effective Dart: Style]:
https://dart.dev/guides/language/effective-dart/style
[CLA]: https://cla.developers.google.com/
[Discord]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Chat.md

flutter_ci_script_beta.sh

@@ -25,6 +25,8 @@ declare -a CODELABS=(
   "haiku_generator"
   "homescreen_codelab"
   "in_app_purchases"
+  # TODO(domesticmouse): Add after beta is above Dart 3.7.0-0
+  # "intro_flutter_gpu"
   "namer"
   # TODO(domesticmouse): Color.red/green/blue are deprecated
   # "next-gen-ui"

flutter_ci_script_master.sh

@@ -25,6 +25,7 @@ declare -a CODELABS=(
   "haiku_generator"
   "homescreen_codelab"
   "in_app_purchases"
+  "intro_flutter_gpu"
   "namer"
   # TODO(domesticmouse): Color.red/green/blue are deprecated
   # "next-gen-ui"

flutter_ci_script_shared.sh

@@ -47,7 +47,19 @@ function ci_codelabs () {
             if [ -d "test" ]
             then
                 if grep -q "flutter:" "pubspec.yaml"; then
-                  flutter test
+
+                    # intro_flutter_gpu only runs with Impeller
+                    if [ $CODELAB = 'intro_flutter_gpu' ]; then
+                        if [ $RUNNER_OS = 'macOS' ] || [ $RUNNER_OS = 'Windows' ]; then
+                            flutter config --enable-native-assets
+                            flutter build `echo $RUNNER_OS | tr '[:upper:]' '[:lower:]'` --debug
+                            flutter test --enable-impeller
+                        else
+                            echo "Skipping $CODELAB on $RUNNER_OS"
+                        fi
+                    else
+                        flutter test
+                    fi
                 else
                   # If the project is not a Flutter project, use the Dart CLI.
                   dart test

flutter_ci_script_stable.sh

@@ -25,6 +25,8 @@ declare -a CODELABS=(
   "haiku_generator"
   "homescreen_codelab"
   "in_app_purchases"
+  # TODO(domesticmouse): Add after stable is above Dart 3.7.0-0
+  # "intro_flutter_gpu"
   "namer"
   "next-gen-ui"
   "testing_codelab"