don't forget to actually return the number of specified test jobs

BUG=741927,743615
TEST=Running browser_tests with the flags below, should print "Using 1 parallel jobs."
--run-manual --ui-test-action-max-timeout=350000 --test-launcher-jobs=1 --test-launcher-bot-mode --test-launcher-print-test-stdio=always
TBR=phajdan.jr@chromium.org

Change-Id: I33f2b4fc54b43ebec8a27c532da17146b42c07cd
Reviewed-on: https://chromium-review.googlesource.com/573380Reviewed-by: Mostyn Bramley-Moore <mostynb@opera.com>
Commit-Queue: Mostyn Bramley-Moore <mostynb@opera.com>
Cr-Commit-Position: refs/heads/master@{#487014}

base/test/launcher/test_launcher.cc

@@ -1204,6 +1204,7 @@ size_t NumParallelJobs() {
       LOG(ERROR) << "Invalid value for " << switches::kTestLauncherJobs;
       return 0U;
     }
+    return jobs;
   } else if (command_line->HasSwitch(kGTestFilterFlag) && !BotModeEnabled()) {
     // Do not run jobs in parallel by default if we are running a subset of
     // the tests and if bot mode is off.