IDL: make optional arguments (without default) explicit sometimes

Source/core/css/CSSStyleSheet.cpp

Index: Source/core/css/CSSStyleSheet.cpp
diff --git a/Source/core/css/CSSStyleSheet.cpp b/Source/core/css/CSSStyleSheet.cpp
index 6add0d9bd607dedfe887bac7410fa41a9551046d..f1116abfd08e90185e910d20bb4bdbe37eb0bf16 100644
--- a/Source/core/css/CSSStyleSheet.cpp
+++ b/Source/core/css/CSSStyleSheet.cpp
@@ -334,7 +334,6 @@ unsigned CSSStyleSheet::insertRule(const String& ruleString, unsigned index, Exc
 
 unsigned CSSStyleSheet::insertRule(const String& rule, ExceptionState& exceptionState)
 {
-    UseCounter::countDeprecation(callingExecutionContext(V8PerIsolateData::mainThreadIsolate()), UseCounter::CSSStyleSheetInsertRuleOptionalArg);
     return insertRule(rule, 0, exceptionState);
 }
 
@@ -357,7 +356,7 @@ void CSSStyleSheet::deleteRule(unsigned index, ExceptionState& exceptionState)
     }
 }
 
-int CSSStyleSheet::addRule(const String& selector, const String& style, int index, ExceptionState& exceptionState)
+int CSSStyleSheet::addRule(const String& selector, const String& style, Optional<int> index, ExceptionState& exceptionState)
 {
     StringBuilder text;
     text.append(selector);
@@ -366,17 +365,12 @@ int CSSStyleSheet::addRule(const String& selector, const String& style, int inde
     if (!style.isEmpty())
         text.append(' ');
     text.append('}');
-    insertRule(text.toString(), index, exceptionState);
+    insertRule(text.toString(), index.isMissing() ? length() : index.get(), exceptionState);
 
     // As per Microsoft documentation, always return -1.
     return -1;
 }
 
-int CSSStyleSheet::addRule(const String& selector, const String& style, ExceptionState& exceptionState)
-{
-    return addRule(selector, style, length(), exceptionState);
-}
-
 
 PassRefPtrWillBeRawPtr<CSSRuleList> CSSStyleSheet::cssRules()
 {