Ensure tests check the return of SpawnChild() when they may wait without timeouts

content/common/sandbox_mac_diraccess_unittest.mm

Index: content/common/sandbox_mac_diraccess_unittest.mm
diff --git a/content/common/sandbox_mac_diraccess_unittest.mm b/content/common/sandbox_mac_diraccess_unittest.mm
index 8aad63bdeaa3d5a51275c6791db9137d26b080b9..b728c64ac8cddd30f9b1ad0fcd3e7a1854a1d989 100644
--- a/content/common/sandbox_mac_diraccess_unittest.mm
+++ b/content/common/sandbox_mac_diraccess_unittest.mm
@@ -35,6 +35,10 @@ class MacDirAccessSandboxTest : public base::MultiProcessTest {
     setenv(kSandboxAccessPathKey, directory_to_try.c_str(), 1);
     base::ProcessHandle child_process = SpawnChild("mac_sandbox_path_access",
                                                    false);
+    if (child_process == base::kNullProcessHandle) {
+      LOG(WARNING) << "SpawnChild failed";
+      return false;
+    }
     int code = -1;
     if (!base::WaitForExitCode(child_process, &code)) {
       LOG(WARNING) << "base::WaitForExitCode failed";