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

Source/core/dom/AttrTest.cpp

Index: Source/core/dom/AttrTest.cpp
diff --git a/Source/core/dom/AttrTest.cpp b/Source/core/dom/AttrTest.cpp
index 7ae6eabfe8cdbe1ca9a8cee5c76fcd232a97d452..85fce9aa8e9b074db2136ce6c855178ce8565ba1 100644
--- a/Source/core/dom/AttrTest.cpp
+++ b/Source/core/dom/AttrTest.cpp
@@ -9,13 +9,11 @@
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
 
-using namespace blink;
-
-namespace {
+namespace blink {
 
 class AttrTest : public ::testing::Test {
 protected:
-    virtual void SetUp() override;
+    void SetUp() override;
 
     PassRefPtrWillBeRawPtr<Attr> createAttribute();
     const AtomicString& value() const { return m_value; }
@@ -82,4 +80,4 @@ TEST_F(AttrTest, LengthOfContents)
     EXPECT_EQ(0u, attr->lengthOfContents());
 }
 
-} // unnamed namespace
+} // namespace blink