Remove support for the LEGACY_CSS_VENDOR_PREFIXES compile-time flag.

Source/WebCore/css/CSSParser.cpp

Index: Source/WebCore/css/CSSParser.cpp
diff --git a/Source/WebCore/css/CSSParser.cpp b/Source/WebCore/css/CSSParser.cpp
index 6faa3d9b6b06948db06f4325ece3aa64d4d1fbec..0386df8bcf0deabb3cd5e379b7b1231b916f577d 100644
--- a/Source/WebCore/css/CSSParser.cpp
+++ b/Source/WebCore/css/CSSParser.cpp
@@ -11782,16 +11782,6 @@ static CSSPropertyID cssPropertyID(const CharacterType* propertyName, unsigned l
 
     const char* name = buffer;
     if (buffer[0] == '-') {
-#if ENABLE(LEGACY_CSS_VENDOR_PREFIXES)
-        // If the prefix is -apple- or -khtml-, change it to -webkit-.
-        // This makes the string one character longer.
-        if (RuntimeEnabledFeatures::legacyCSSVendorPrefixesEnabled()
-            && (hasPrefix(buffer, length, "-apple-") || hasPrefix(buffer, length, "-khtml-"))) {
-            memmove(buffer + 7, buffer + 6, length + 1 - 6);
-            memcpy(buffer, "-webkit", 7);
-            ++length;
-        }
-#endif
 #if PLATFORM(IOS)
         cssPropertyNameIOSAliasing(buffer, name, length);
 #endif