Add --enable-isolate-groups to allowed flags in switches.cc (#21149)

This will allow customers to try out the lightweight isolate support in the Dart VM in AOT mode.

To be future proof, we also add the negative flags to the allow list, thereby allowing the Dart VM to
change the default in the future, while still allowing customers to opt out.

Issue b/158554251

shell/common/shell_unittests.cc

@@ -93,6 +93,30 @@ static void ValidateDestroyPlatformView(Shell* shell) {
   ASSERT_FALSE(RasterizerHasLayerTree(shell));
 }
 
+static std::string CreateFlagsString(std::vector<const char*>& flags) {
+  if (flags.size() == 0) {
+    return "";
+  }
+  std::string flags_string = flags[0];
+  for (size_t i = 1; i < flags.size(); ++i) {
+    flags_string += ",";
+    flags_string += flags[i];
+  }
+  return flags_string;
+}
+
+static void TestDartVmFlags(std::vector<const char*>& flags) {
+  std::string flags_string = CreateFlagsString(flags);
+  const std::vector<fml::CommandLine::Option> options = {
+      fml::CommandLine::Option("dart-flags", flags_string)};
+  fml::CommandLine command_line("", options, std::vector<std::string>());
+  flutter::Settings settings = flutter::SettingsFromCommandLine(command_line);
+  EXPECT_EQ(settings.dart_flags.size(), flags.size());
+  for (size_t i = 0; i < flags.size(); ++i) {
+    EXPECT_EQ(settings.dart_flags[i], flags[i]);
+  }
+}
+
 TEST_F(ShellTest, InitializeWithInvalidThreads) {
   ASSERT_FALSE(DartVMRef::IsInstanceRunning());
   Settings settings = CreateSettingsForFixture();
@@ -275,25 +299,6 @@ TEST_F(ShellTest, LastEntrypoint) {
   ASSERT_FALSE(DartVMRef::IsInstanceRunning());
 }
 
-TEST(ShellTestNoFixture, EnableMirrorsIsAllowed) {
-  if (DartVM::IsRunningPrecompiledCode()) {
-    // This covers profile and release modes which use AOT (where this flag does
-    // not make sense anyway).
-    GTEST_SKIP();
-    return;
-  }
-#if FLUTTER_RELEASE
-  GTEST_SKIP();
-  return;
-#endif
-
-  const std::vector<fml::CommandLine::Option> options = {
-      fml::CommandLine::Option("dart-flags", "--enable_mirrors")};
-  fml::CommandLine command_line("", options, std::vector<std::string>());
-  flutter::Settings settings = flutter::SettingsFromCommandLine(command_line);
-  EXPECT_EQ(settings.dart_flags.size(), 1u);
-}
-
 TEST_F(ShellTest, DisallowedDartVMFlag) {
   // Run this test in a thread-safe manner, otherwise gtest will complain.
   ::testing::FLAGS_gtest_death_test_style = "threadsafe";
@@ -309,22 +314,18 @@ TEST_F(ShellTest, DisallowedDartVMFlag) {
 }
 
 TEST_F(ShellTest, AllowedDartVMFlag) {
-  const std::vector<fml::CommandLine::Option> options = {
-#if !FLUTTER_RELEASE
-    fml::CommandLine::Option("dart-flags",
-                             "--max_profile_depth 1,--random_seed 42")
-#endif
+  std::vector<const char*> flags = {
+      "--enable-isolate-groups",
+      "--no-enable-isolate-groups",
   };
-  fml::CommandLine command_line("", options, std::vector<std::string>());
-  flutter::Settings settings = flutter::SettingsFromCommandLine(command_line);
-
 #if !FLUTTER_RELEASE
-  EXPECT_EQ(settings.dart_flags.size(), 2u);
-  EXPECT_EQ(settings.dart_flags[0], "--max_profile_depth 1");
-  EXPECT_EQ(settings.dart_flags[1], "--random_seed 42");
-#else
-  EXPECT_EQ(settings.dart_flags.size(), 0u);
+  flags.push_back("--max_profile_depth 1");
+  flags.push_back("--random_seed 42");
+  if (!DartVM::IsRunningPrecompiledCode()) {
+    flags.push_back("--enable_mirrors");
+  }
 #endif
+  TestDartVmFlags(flags);
 }
 
 TEST_F(ShellTest, NoNeedToReportTimingsByDefault) {

shell/common/switches.cc

@@ -42,6 +42,8 @@ struct SwitchDesc {
 
 // clang-format off
 static const std::string gAllowedDartFlags[] = {
+    "--enable-isolate-groups",
+    "--no-enable-isolate-groups",
     "--no-causal_async_stacks",
     "--lazy_async_stacks",
 };
@@ -51,6 +53,8 @@ static const std::string gAllowedDartFlags[] = {
 
 // clang-format off
 static const std::string gAllowedDartFlags[] = {
+    "--enable-isolate-groups",
+    "--no-enable-isolate-groups",
     "--enable_mirrors",
     "--enable-service-port-fallback",
     "--lazy_async_stacks",