Move ForkWithFlags from sandbox/ to base/ and plug it into LaunchProcess.

base/process/process_util_unittest.cc

Index: base/process/process_util_unittest.cc
diff --git a/base/process/process_util_unittest.cc b/base/process/process_util_unittest.cc
index af88fe1fd3a01f2ce3c10427e77b26645ba6eda8..0f6b75dddb437fe866fe90baab033bdfdb9a48f6 100644
--- a/base/process/process_util_unittest.cc
+++ b/base/process/process_util_unittest.cc
@@ -684,10 +684,8 @@ TEST_F(ProcessUtilTest, LaunchProcess) {
   // Test a non-trival value for clone_flags.
   // Don't test on Valgrind as it has limited support for clone().
   if (!RunningOnValgrind()) {
-    EXPECT_EQ(
-        "wibble\n",
-        TestLaunchProcess(
-            echo_base_test, env_changes, no_clear_environ, CLONE_FS | SIGCHLD));
+    EXPECT_EQ("wibble\n", TestLaunchProcess(echo_base_test, env_changes,
+                                            no_clear_environ, CLONE_FS));
   }
 
   EXPECT_EQ(