Rename 'instant' value of scroll-behavior CSS property to 'auto'

Source/core/css/parser/CSSParserFastPaths.cpp

Index: Source/core/css/parser/CSSParserFastPaths.cpp
diff --git a/Source/core/css/parser/CSSParserFastPaths.cpp b/Source/core/css/parser/CSSParserFastPaths.cpp
index a57879a6f3dec0b365184dccb4e2fc7da06c9116..d25f71a109cfdb36cfadf2837d1f2e35114bfad7 100644
--- a/Source/core/css/parser/CSSParserFastPaths.cpp
+++ b/Source/core/css/parser/CSSParserFastPaths.cpp
@@ -245,9 +245,9 @@ bool CSSParserFastPaths::isValidKeywordPropertyAndValue(CSSPropertyID propertyId
         return valueID == CSSValueStatic || valueID == CSSValueRelative || valueID == CSSValueAbsolute || valueID == CSSValueFixed;
     case CSSPropertyResize: // none | both | horizontal | vertical | auto
         return valueID == CSSValueNone || valueID == CSSValueBoth || valueID == CSSValueHorizontal || valueID == CSSValueVertical || valueID == CSSValueAuto;
-    case CSSPropertyScrollBehavior: // instant | smooth
+    case CSSPropertyScrollBehavior: // auto | smooth
         ASSERT(RuntimeEnabledFeatures::cssomSmoothScrollEnabled());
-        return valueID == CSSValueInstant || valueID == CSSValueSmooth;
+        return valueID == CSSValueAuto || valueID == CSSValueSmooth;
     case CSSPropertySpeak: // none | normal | spell-out | digits | literal-punctuation | no-punctuation
         return valueID == CSSValueNone || valueID == CSSValueNormal || valueID == CSSValueSpellOut || valueID == CSSValueDigits || valueID == CSSValueLiteralPunctuation || valueID == CSSValueNoPunctuation;
     case CSSPropertyTableLayout: // auto | fixed