Have JsInliner refuse to interpose a new expression
before a substituted argument.

Review at http://gwt-code-reviews.appspot.com/344801

Review by: scottb@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@7913 8db76d5a-ed1c-0410-87a9-c151d255dfc7