Bug 1378011 (part 2) - Remove the Legacy HTML Parser's EntityToUnicode conversions. r=mrbkap.

It's unused except in test code (nsTestEntityTable). The patch removes that
test code, which also removes testing for UnicodeToEntity conversion, but the
test code wasn't being run anyway so it's no great loss.

(UnicodeToEntity conversion is still used by
nsHTMLContentSerializer::AppendAndTranslateEntities().)

parser/htmlparser/nsParserService.cpp

@@ -52,15 +52,6 @@ nsParserService::HTMLIdToAtomTag(int32_t aId) const
   return nsHTMLTags::GetAtom((nsHTMLTag)aId);
 }
 
-NS_IMETHODIMP
-nsParserService::HTMLConvertEntityToUnicode(const nsAString& aEntity,
-                                            int32_t* aUnicode) const
-{
-  *aUnicode = nsHTMLEntities::EntityToUnicode(aEntity);
-
-  return NS_OK;
-}
-
 NS_IMETHODIMP
 nsParserService::HTMLConvertUnicodeToEntity(int32_t aUnicode,
                                             nsCString& aEntity) const