Ensures EntryMethods are traversed first.

Previously GWT happened to process GWT.create() calls in EntryMethods, 
before GWT.create() calls in other places. This was never promised 
behavior but some apps now depend on it.

This change ensures that this behavior is honored even within the new 
incremental compile path.

Change-Id: Id36e91fa455fd95394a6a02ab0356de7053890a6
Review-Link: https://gwt-review.googlesource.com/#/c/10410/