Fix unit test style in core/{dom,editing,html}/.

Source/core/dom/RangeTest.cpp

Index: Source/core/dom/RangeTest.cpp
diff --git a/Source/core/dom/RangeTest.cpp b/Source/core/dom/RangeTest.cpp
index dca0f366772a7dc8ecba1e5f555e8c185a6027e8..58629bd3485312634c73781af571447ecdaeae7d 100644
--- a/Source/core/dom/RangeTest.cpp
+++ b/Source/core/dom/RangeTest.cpp
@@ -19,13 +19,11 @@
 #include "wtf/text/AtomicString.h"
 #include <gtest/gtest.h>
 
-using namespace blink;
-
-namespace {
+namespace blink {
 
 class RangeTest : public ::testing::Test {
 protected:
-    virtual void SetUp() override;
+    void SetUp() override;
 
     HTMLDocument& document() const;
 
@@ -141,4 +139,4 @@ TEST_F(RangeTest, SplitTextNodeRangeOutsideText)
     EXPECT_EQ(4, rangeFromTextToMiddleOfElement->endOffset());
 }
 
-}
+} // namespace blink