add safari desktop to web engine tests.

https://github.com/flutter/flutter/issues/58012 -> I'll close this issue after merging this CL and this PR: https://github.com/flutter/engine/pull/21228

Change-Id: Idb3c2b16f7ac0320b74b873ba72ce3ff1ea87e28
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/6600
Commit-Queue: Nurhan Turgut <nurhan@google.com>
Reviewed-by: Christopher Fujino <fujino@google.com>

recipes/web_engine.expected/mac-post-submit.json

diff --git a/recipes/web_engine.expected/mac-post-submit.json b/recipes/web_engine.expected/mac-post-submit.json
index 5ca75a8..7665521 100644
--- a/recipes/web_engine.expected/mac-post-submit.json
+++ b/recipes/web_engine.expected/mac-post-submit.json
@@ -858,6 +858,36 @@
   },
   {
     "cmd": [
+      "[CACHE]/builder/src/out/host_debug_unopt/dart-sdk/bin/dart",
+      "dev/felt.dart",
+      "test",
+      "--browser",
+      "safari"
+    ],
+    "cwd": "[CACHE]/builder/src/flutter/lib/web_ui",
+    "env": {
+      "ANDROID_HOME": "[CACHE]/builder/src/third_party/android_tools/sdk",
+      "CHROME_NO_SANDBOX": "true",
+      "ENGINE_PATH": "[CACHE]/builder",
+      "GOMA_DIR": "[CACHE]/goma/client"
+    },
+    "env_prefixes": {
+      "PATH": [
+        "[CACHE]/builder/src/third_party/dart/tools/sdks/dart-sdk/bin"
+      ]
+    },
+    "env_suffixes": {
+      "DEPOT_TOOLS_UPDATE": [
+        "0"
+      ],
+      "PATH": [
+        "RECIPE_REPO[depot_tools]"
+      ]
+    },
+    "name": "felt test safari desktop"
+  },
+  {
+    "cmd": [
       "cipd",
       "ensure",
       "-root",

recipes/web_engine.py

diff --git a/recipes/web_engine.py b/recipes/web_engine.py
index 9c0e2b4..7d5f4ae 100644
--- a/recipes/web_engine.py
+++ b/recipes/web_engine.py
@@ -214,6 +214,11 @@
       if api.platform.is_mac:
         chrome_path = checkout.join('flutter', 'lib', 'web_ui', '.dart_tool',
                                        'chrome', '768985')
+        additional_args_safari_desktop = ['--browser', 'safari']
+        felt_test_safari_desktop = copy.deepcopy(felt_cmd)
+        felt_test_safari_desktop.append('test')
+        felt_test_safari_desktop.extend(additional_args_safari_desktop)
+        api.step('felt test safari desktop', felt_test_safari_desktop)
       if api.platform.is_linux:
         web_engine_analysis_cmd = [
             checkout.join('flutter', 'lib', 'web_ui', 'dev', 'web_engine_analysis.sh'),