Change users of Length() to IsEmpty() where the code really cares about

the latter in content/.  Bug 100649, r=jag, sr=jst


git-svn-id: svn://10.0.0.236/trunk@112623 18797224-902f-48f8-a5cc-f745e15eee43

mozilla/content/base/src/nsHTMLContentSerializer.cpp

@@ -701,7 +701,7 @@ nsHTMLContentSerializer::AppendToString(const nsAReadableString& aStr,
           } else if (mIsLatin1 && val > 127 && val < 256) {
             parserService->HTMLConvertUnicodeToEntity(val, entityReplacement);
 
-            if (entityReplacement.Length() > 0) {
+            if (!entityReplacement.IsEmpty()) {
               entityText = entityReplacement.get();
               break;
             }