ISSUE-373: Refine how multiple role values in one role attribute should be processed

Another use case to consider: A landmark role and a widget role on the same element. A landmark role is used primarily to indicate structure as opposed to a widget role which indicates the functionality of an element. This type of combination should be supported.

As a specific example in Dojo, you cannot specify a landmark role on the same <div> that has a Dojo widget or container role, because Dojo automatically appends the widget role in front of the landmark role. The landmark role will then be ignored, and the programmer is thinking that they implemented the landmarks correctly. <div role='main' dojoType='dijit.layout.ContentPane'>, will change to be something like <div role='group main' dojoType='dijit.layout.ContentPane'> and will also add Dojo classes and other attributes.

To fix this, programmers must carefully consider how to add in another <div> because some Dojo elements inherit the region and other formatting information from its direct descendants in the code. If you add a <div role='main'> in between them, the inherited formatting won't work properly. This makes landmark roles more tricky to implement and will likely introduce unintended bugs where the developer is trying to add WAI-ARIA.