Optimize StringImpl::lower() for 8-bit strings

Source/wtf/text/WTFStringTest.cpp

 /*
  * Copyright (C) 2012 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 321 matching lines @@
     String nonASCII = String::fromUTF8("LIN\xE2\x84\xAA");
     EXPECT_FALSE(startsWithIgnoringASCIICase(allASCII, nonASCII));
     EXPECT_TRUE(startsWithIgnoringASCIICase(allASCII, nonASCII.lower()));
 
     EXPECT_FALSE(startsWithIgnoringASCIICase(nonASCII, allASCII));
     EXPECT_FALSE(startsWithIgnoringASCIICase(nonASCII, allASCIILowerCase));
     EXPECT_FALSE(startsWithIgnoringASCIICase(nonASCII, allASCIIMixedCase));
     EXPECT_FALSE(startsWithIgnoringASCIICase(nonASCII, allASCIIDifferent));
 }
 
+TEST(StringTest, Lower)
+{
+    EXPECT_STREQ("link", String("LINK").lower().ascii().data());
+    EXPECT_STREQ("link", String("lInk").lower().ascii().data());
+    EXPECT_STREQ("lin\xE1k", String("lIn\xC1k").lower().latin1().data());
+    EXPECT_STREQ("link", String::fromUTF8("LIN\xE2\x84\xAA").lower().utf8().data());
+}
+
 } // namespace WTF