Prevent direct use of "replacement" text encoding.

Source/wtf/text/TextCodecReplacementTest.cpp

Index: Source/wtf/text/TextCodecReplacementTest.cpp
diff --git a/Source/wtf/text/TextCodecReplacementTest.cpp b/Source/wtf/text/TextCodecReplacementTest.cpp
index b95eec8b75249af91136ecaf821e74a59eb3db60..6d3d1a69c0bdc8b1fa08a4933ff2b34780c381e0 100644
--- a/Source/wtf/text/TextCodecReplacementTest.cpp
+++ b/Source/wtf/text/TextCodecReplacementTest.cpp
@@ -23,10 +23,9 @@ const char* replacementAlias = "iso-2022-kr";
 
 TEST(TextCodecReplacement, Aliases)
 {
-    // FIXME: The 'replacement' label itself should not be referenceable by
-    // resources or script - it's a specification convenience - but much of
-    // the wtf/text API asserts that an encoding name is a label for itself.
-    // crbug.com/277037
+    // "replacement" is not a valid alias for itself
+    EXPECT_FALSE(TextEncoding("replacement").isValid());
+    EXPECT_FALSE(TextEncoding("rEpLaCeMeNt").isValid());
 
     EXPECT_TRUE(TextEncoding(replacementAlias).isValid());
     EXPECT_STREQ("replacement", TextEncoding(replacementAlias).name());