Fix launching an app via the shim.

http://crrev.com/21005003 introduced a regression where app shims
launched with no files (the default case) do not actually launch the
app.

This CL checks whether any files were passed in and, if not, launches
the app with no launch data.

BUG=168080,292566
TEST=Starting an app shim should start the app.

Review URL: https://chromiumcodereview.appspot.com/24353002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@224690 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 224690