Make d8-os test less flaky.

Because of stress testing there may be parallel instances of the test
running, which makes it fail when using a hardcoded test dir
name. Adding a random suffix helps. It'd be nicer to add something
like pid, but there doesn't seem to be an easy way of getting it.

R=yangguo@chromium.org

Review URL: http://codereview.chromium.org/7491057

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8848 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

test/mjsunit/d8-os.js

@@ -30,6 +30,9 @@
 // implemented on Windows, and even if it were then many of the things
 // we are calling would not be available.
 
+var TEST_DIR = "d8-os-test-directory-" + ((Math.random() * (1<<30)) | 0);
+
+
 function arg_error(str) {
   try {
     eval(str);
@@ -53,14 +56,15 @@ function str_error(str) {
 if (this.os && os.system) {
   try {
     // Delete the dir if it is lying around from last time.
-    os.system("ls", ["d8-os-test-directory"]);
-    os.system("rm", ["-r", "d8-os-test-directory"]);
+    os.system("ls", [TEST_DIR]);
+    os.system("rm", ["-r", TEST_DIR]);
   } catch (e) {
   }
-  os.mkdirp("d8-os-test-directory");
-  os.chdir("d8-os-test-directory");
+  os.mkdirp(TEST_DIR);
+  os.chdir(TEST_DIR);
+  try {
     // Check the chdir worked.
-  os.system('ls', ['../d8-os-test-directory']);
+    os.system('ls', ['../' + TEST_DIR]);
     // Simple create dir.
     os.mkdirp("dir");
     // Create dir in dir.
@@ -139,9 +143,10 @@ if (this.os && os.system) {
       assertEquals("baz\n", os.system("echo", ["baz"]));
       //}
     }
-
+  } finally {
     os.chdir("..");
-  os.system("rm", ["-r", "d8-os-test-directory"]);
+    os.system("rm", ["-r", TEST_DIR]);
+  }
 
   // Too few args.
   arg_error("os.umask();");