mojo: fix little bug in DynamicServiceLoader/Runner

If the Runner wasn't actually told to Start(), the DelegateSimpleThread would
DCHECK for not having been Started. This patch makes it so we don't allocate
a DST unless we need to.

Also adds basic unittest files for DynamicServiceLoader and Runner.

BUG=

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=285650

Review URL: https://codereview.chromium.org/414173004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@285849 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/mojo/mojo.gyp b/mojo/mojo.gyp
index 1e60ea01..0cec913 100644
--- a/mojo/mojo.gyp
+++ b/mojo/mojo.gyp
@@ -690,6 +690,8 @@
       ],
       'sources': [
         'shell/child_process_host_unittest.cc',
+        'shell/dynamic_service_loader_unittest.cc',
+        'shell/in_process_dynamic_service_runner_unittest.cc',
         'shell/shell_test_base.cc',
         'shell/shell_test_base.h',
         'shell/shell_test_base_unittest.cc',