Setuid sandbox unittest: fix environment.

sandbox/linux/suid/client/setuid_sandbox_client_unittest.cc

Index: sandbox/linux/suid/client/setuid_sandbox_client_unittest.cc
diff --git a/sandbox/linux/suid/client/setuid_sandbox_client_unittest.cc b/sandbox/linux/suid/client/setuid_sandbox_client_unittest.cc
index 764ccb10f68e3ff9f189e39ddf14948824e61e21..135e7fc07807918bd83b8b15528fb88e94c0e011 100644
--- a/sandbox/linux/suid/client/setuid_sandbox_client_unittest.cc
+++ b/sandbox/linux/suid/client/setuid_sandbox_client_unittest.cc
@@ -18,6 +18,10 @@ TEST(SetuidSandboxClient, SetupLaunchEnvironment) {
   scoped_ptr<base::Environment> env(base::Environment::Create());
   EXPECT_TRUE(env != NULL);
 
+  std::string saved_ld_preload;
+  bool environment_had_ld_preload;
+  // First, back-up the real LD_PRELOAD if any.
+  environment_had_ld_preload = env->GetVar("LD_PRELOAD", &saved_ld_preload);
   // Setup environment variables to save or not save.
   EXPECT_TRUE(env->SetVar("LD_PRELOAD", kTestValue));
   EXPECT_TRUE(env->UnSetVar("LD_ORIGIN_PATH"));
@@ -46,6 +50,14 @@ TEST(SetuidSandboxClient, SetupLaunchEnvironment) {
 
   // Check that LD_ORIGIN_PATH was not saved.
   EXPECT_FALSE(env->HasVar("SANDBOX_LD_ORIGIN_PATH"));
+
+  // We should not forget to restore LD_PRELOAD at the end, or this environment
+  // variable will affect the next running tests!
+  if (environment_had_ld_preload) {
+    EXPECT_TRUE(env->SetVar("LD_PRELOAD", saved_ld_preload));
+  } else {
+    EXPECT_TRUE(env->UnSetVar("LD_PRELOAD"));
+  }
 }
 
 TEST(SetuidSandboxClient, SandboxedClientAPI) {