Current server state saving implementation prevents multi-window usage

Problem:

open two tabs (or windows) in browser with view:

<h:body>
<h:form id="formId">
<h:commandButton value="Click me 20x!" />
</h:form>
</h:body>

then click the button on the first tab 20x or more -> then click the button on the second tab -> you will get the most beloved ViewExpiredException.

Reason:
oam.SerializedViewCollection drops the saved state for 2. tab from map.

Suggestion:
remove the successfully restored view state from map. This can be done, because each SerializedViewKey is unique over all requests for one HttpSession - see DefaultFaceletsStateManagementHelper.nextViewSequence(FacesContext). Because each request has unique sequence number, we can the "just restored" one remove from the map, because it can never come from client again.

Open question: the previous statement is true except the double submit problem: JAVASERVERFACES_SPEC_PUBLIC-559. In this case, server can process same request (with the same sequence number) twice.