Revert "--sound-null-safety instead of enable-experiment where possible (#26999)" (#27059)

This reverts commit 3283cafe.

lib/snapshot/BUILD.gn

@@ -46,7 +46,7 @@ compiled_action("generate_snapshot_bin") {
   ]
 
   args = [
-    "--sound-null-safety",
+    "--enable-experiment=non-nullable",
     "--snapshot_kind=core",
     "--enable_mirrors=false",
     "--vm_snapshot_data=" + rebase_path(vm_snapshot_data),

testing/run_tests.py

@@ -233,7 +233,8 @@ def SnapshotTest(build_dir, test_packages, dart_file, kernel_file_output, verbos
     dart,
     '--disable-dart-dev',
     frontend_server,
-    '--sound-null-safety',
+    '--enable-experiment=non-nullable',
+    '--no-sound-null-safety',
     '--sdk-root',
     flutter_patched_sdk,
     '--incremental',

testing/testing.gni

@@ -80,7 +80,7 @@ template("dart_snapshot_kernel") {
       rebase_path("$root_out_dir/flutter_patched_sdk"),
       "--target",
       "flutter",
-      "--sound-null-safety",
+      "--enable-experiment=non-nullable",
       "--output-dill",
       rebase_path(invoker.dart_kernel, root_out_dir),
       "--depfile",

web_sdk/BUILD.gn

@@ -116,7 +116,7 @@ prebuilt_dart_action("flutter_dartdevc_kernel_sdk_outline") {
   script = "//third_party/dart/utils/bazel/kernel_worker.dart"
 
   args = [
-    "--sound-null-safety",
+    "--enable-experiment=non-nullable",
     "--summary-only",
     "--target",
     "ddc",
@@ -162,7 +162,7 @@ prebuilt_dart_action("flutter_dartdevc_kernel_sdk") {
   ]
 
   args = [
-    "--sound-null-safety",
+    "--enable-experiment=non-nullable",
     "--compile-sdk",
     "dart:core",
 
@@ -215,7 +215,7 @@ prebuilt_dart_action("flutter_dartdevc_canvaskit_kernel_sdk") {
   ]
 
   args = [
-    "--sound-null-safety",
+    "--enable-experiment=non-nullable",
     "--compile-sdk",
     "dart:core",
 
@@ -270,7 +270,7 @@ prebuilt_dart_action("flutter_dartdevc_canvaskit_html_kernel_sdk") {
   ]
 
   args = [
-    "--sound-null-safety",
+    "--enable-experiment=non-nullable",
     "--compile-sdk",
     "dart:core",
 
@@ -325,6 +325,7 @@ prebuilt_dart_action("flutter_dartdevc_kernel_sdk_sound") {
   ]
 
   args = [
+    "--enable-experiment=non-nullable",
     "--sound-null-safety",
     "--compile-sdk",
     "dart:core",
@@ -379,6 +380,7 @@ prebuilt_dart_action("flutter_dartdevc_canvaskit_kernel_sdk_sound") {
   ]
 
   args = [
+    "--enable-experiment=non-nullable",
     "--sound-null-safety",
     "--compile-sdk",
     "dart:core",
@@ -434,6 +436,7 @@ prebuilt_dart_action("flutter_dartdevc_canvaskit_html_kernel_sdk_sound") {
   ]
 
   args = [
+    "--enable-experiment=non-nullable",
     "--sound-null-safety",
     "--compile-sdk",
     "dart:core",
@@ -484,6 +487,7 @@ prebuilt_dart_action("flutter_dartdevc_kernel_sdk_outline_sound") {
   script = "//third_party/dart/utils/bazel/kernel_worker.dart"
 
   args = [
+    "--enable-experiment=non-nullable",
     "--sound-null-safety",
     "--summary-only",
     "--target",