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

Source/wtf/text/WTFStringTest.cpp

Index: Source/wtf/text/WTFStringTest.cpp
diff --git a/Source/wtf/text/WTFStringTest.cpp b/Source/wtf/text/WTFStringTest.cpp
index 26f882e5faa176193b583962342fc13bb81b63bf..f3ab0730b697c3e03b8b4869167068da42432525 100644
--- a/Source/wtf/text/WTFStringTest.cpp
+++ b/Source/wtf/text/WTFStringTest.cpp
@@ -335,4 +335,12 @@ TEST(WTF, StartsWithIgnoringASCIICase)
     EXPECT_FALSE(startsWithIgnoringASCIICase(nonASCII, allASCIIDifferent));
 }
 
+TEST(WTFString, lower)

[tkent, 2015/06/15 01:12:56]

TEST(StringTest, Lower)

+{
+    ASSERT_STREQ("link", String("LINK").lower().ascii().data());

[tkent, 2015/06/15 01:12:56]

Use EXPECT_STREQ.
Same for the following lines.

+    ASSERT_STREQ("link", String("lInk").lower().ascii().data());
+    ASSERT_STREQ("lin\xE1k", String("lIn\xC1k").lower().latin1().data());
+    ASSERT_STREQ("link", String::fromUTF8("LIN\xE2\x84\xAA").lower().utf8().data());
+}
+
 } // namespace