AU/unittest: parameterize test_http_server port

This eliminates the constant definition of the test HTTP server port,
replacing it with a command-line parameter (which defaults to 8080, the
well-known userland HTTP port). This is needed for allowing parallel
invocations of unit tests.

BUG=chromium:236465
TEST=Passes unit tests

Change-Id: I91904dc360ec1b993cbaae93554fb0dd9e5adaad
Reviewed-on: https://gerrit.chromium.org/gerrit/60626
Tested-by: Gilad Arnold <garnold@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Commit-Queue: Gilad Arnold <garnold@chromium.org>
diff --git a/subprocess_unittest.cc b/subprocess_unittest.cc
index d23040d..427f7e3 100644
--- a/subprocess_unittest.cc
+++ b/subprocess_unittest.cc
@@ -114,6 +114,7 @@
   CancelTestData* cancel_test_data = reinterpret_cast<CancelTestData*>(data);
   vector<string> cmd;
   cmd.push_back("./test_http_server");
+  cmd.push_back(StringPrintf("%d", kLocalHttpPort));
   uint32_t tag = Subprocess::Get().Exec(cmd, CallbackBad, NULL);
   EXPECT_NE(0, tag);
   cancel_test_data->spawned = true;