[Windows] Reenable LowBox AppContainer Tests.

This CL reenables two tests which were disabled due to failing on ARM64.
These tests don't require the creation of an AppContainer profile, so
they've been converted to standalone tests rather than using the test
fixture class as a base.

Bug: 352720904
Change-Id: I6f18bfa4b9c10108e1b7a2581b66e9e155bc53a8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5717776
Reviewed-by: Will Harris <wfh@chromium.org>
Commit-Queue: James Forshaw <forshaw@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1329754}

sandbox/win/src/app_container_test.cc

@@ -260,8 +260,7 @@ SBOX_TESTS_COMMAND int AppContainerEvent_Open(int argc, wchar_t** argv) {
   return SBOX_TEST_FAILED;
 }
 
-// TODO: crbug.com/352478202 - Enable again once the test is no longer flaky.
-TEST_F(AppContainerTest, DISABLED_DenyOpenEventForLowBox) {
+TEST(LowBoxTest, DenyOpenEventForLowBox) {
   if (!features::IsAppContainerSandboxSupported())
     return;
 
@@ -531,20 +530,19 @@ TEST(AppContainerLaunchTest, CreateTempFileNoFirewall) {
   EXPECT_TRUE(AppContainerBase::DeleteNoFirewall(package_name.c_str()));
 }
 
-// TODO: crbug.com/352478202 - Enable again once the test is no longer flaky.
-TEST_F(AppContainerTest, DISABLED_ChildProcessMitigationLowBox) {
+TEST(LowBoxTest, ChildProcessMitigationLowBox) {
   if (!features::IsAppContainerSandboxSupported()) {
     return;
   }
 
   TestRunner runner(JobLevel::kUnprotected, USER_UNPROTECTED, USER_UNPROTECTED);
 
-#if defined(ARCH_CPU_ARM64) && !defined(NDEBUG)
+#if defined(ARCH_CPU_ARM64)
   // TODO(crbug.com/41497342) A DPLOG issued when CreateProcess() fails
   // conflicts with Csrss lockdown on Win11 ARM64 - so allow Csrss to allow the
   // process to run the right exitcode and not an access violation crash.
   runner.SetDisableCsrss(false);
-#endif  // defined(ARCH_CPU_ARM64) && !defined(NDEBUG)
+#endif  // defined(ARCH_CPU_ARM64)
 
   EXPECT_EQ(SBOX_ALL_OK,
             runner.GetPolicy()->GetConfig()->SetLowBox(kAppContainerSid));