sandbox: run Credentials.CanDetectRoot as a SANDBOX_TEST

sandbox/linux/services/credentials_unittest.cc

Index: sandbox/linux/services/credentials_unittest.cc
diff --git a/sandbox/linux/services/credentials_unittest.cc b/sandbox/linux/services/credentials_unittest.cc
index 1209fdf295f4acd6c8b2e916041b4fa689d82a01..40a2bc45f7ebae0cac6890c0ddfb28e72d758e75 100644
--- a/sandbox/linux/services/credentials_unittest.cc
+++ b/sandbox/linux/services/credentials_unittest.cc
@@ -123,11 +123,11 @@ SANDBOX_TEST(Credentials, NestedUserNS) {
 }
 
 // Test the WorkingDirectoryIsRoot() helper.
-TEST(Credentials, CanDetectRoot) {
-  ASSERT_EQ(0, chdir("/proc/"));
-  ASSERT_FALSE(WorkingDirectoryIsRoot());
-  ASSERT_EQ(0, chdir("/"));
-  ASSERT_TRUE(WorkingDirectoryIsRoot());
+SANDBOX_TEST(Credentials, CanDetectRoot) {
+  PCHECK(0 == chdir("/proc/"));

[jln (very slow on Chromium), 2015/02/04 23:24:28]

Note: we have SANDBOX_ASSERT_EQ() etc for these. (But this prints errno so,
good.)

+  CHECK(!WorkingDirectoryIsRoot());
+  PCHECK(0 == chdir("/"));
+  CHECK(WorkingDirectoryIsRoot());
 }
 
 // Disabled on ASAN because of crbug.com/451603.