fix(ngMessageFormat): ensure bindings are valid for Protractor

[petebacondarwin]

Yes, yes, I know. This PR requires unit tests, etc, etc.
Just pushing here for @chirayuk to take care of. Thanks @chirayuk !

[petebacondarwin]

To recreate the issue we just need to have an ICU plural message interpolation, the run a protractor spec that tries to find an element by a binding....

      {{ app.filteredRestaurants.length, plural,
        =0 {No restaurants found!}
        =1 {Only one restaurant found!}
        other {# restaurants found.}
      }}

    var userNameDisplay = element(by.binding('app.user.name'));

The call to by.binding('...') triggers a call in angular.js of testability.findBindings which tries to find the expression in the binding name:

if (bindingName.indexOf(expression) != -1) {

But without this fix we have a binding that consists of an array with on undefined item.

[chirayuk]

Thanks. I'll work on this PR in the next hour or so!

[chirayuk]

I'm waiting for Travis status. However, I think this one is good to merge once it's confirmed to pass on Travis. See #11649 which has the changes to the test files and some symbol renaming protection. (Please merge that one if I go to bed before I'm able to merge this.)