Allow rulesets to be different in Firefox and Chrome releases
Working around#5196 is going to require a temporary divergence in the GoogleAPIs ruleset in order to work around a Chrome bug.
Right now I can think of two ways to do this. One is to add a new attribute to elements which specifies that the only work on some platforms. Another is to build the Chrome releases from a different git branch.
The new rule element is probably slightly more elegant, and also slightly more work.