Simplify WTF::base64Decode() after r154538

Source/core/page/DOMWindowBase64.cpp

Index: Source/core/page/DOMWindowBase64.cpp
diff --git a/Source/core/page/DOMWindowBase64.cpp b/Source/core/page/DOMWindowBase64.cpp
index 78c0ea1a51a69c6cc2d3253687d1dc3168fd3572..6411d1421358318067454df7e9402f115939e880 100644
--- a/Source/core/page/DOMWindowBase64.cpp
+++ b/Source/core/page/DOMWindowBase64.cpp
@@ -65,7 +65,7 @@ String atob(void*, const String& encodedString, ExceptionState& es)
     }
 
     Vector<char> out;
-    if (!base64Decode(encodedString, out, Base64FailOnInvalidCharacter, Base64StrictPaddingValidation)) {
+    if (!base64Decode(encodedString, out, Base64FailOnInvalidCharacterOrExcessPadding)) {
         es.throwDOMException(InvalidCharacterError, "'atob' failed: The string to be decoded is not correctly encoded.");
         return String();
     }