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

Source/core/dom/NthIndexCacheTest.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/dom/NthIndexCache.h"
 
 #include "core/dom/Document.h"
 #include "core/html/HTMLElement.h"
 #include "core/testing/DummyPageHolder.h"
 #include <gtest/gtest.h>
 
-using namespace blink;
-
-namespace {
+namespace blink {
 
 class NthIndexCacheTest : public ::testing::Test {
-
 protected:
-    virtual void SetUp() override;
+    void SetUp() override;
 
     Document& document() const { return m_dummyPageHolder->document(); }
     void setHtmlInnerHTML(const char* htmlContent);
 
 private:
     OwnPtr<DummyPageHolder> m_dummyPageHolder;
 };
 
 void NthIndexCacheTest::SetUp()
 {
@@ skipping 11 matching lines @@
         "<span></span><span></span><span></span><span></span><span></span>"
         "<span></span><span></span><span></span><span></span><span id=last></span>"
         "</body>", ASSERT_NO_EXCEPTION);
 
     NthIndexCache nthIndexCache(document());
 
     EXPECT_EQ(nthIndexCache.nthChildIndex(*document().getElementById("nth-child")), 12U);
     EXPECT_EQ(nthIndexCache.nthLastChildIndex(*document().getElementById("nth-last-child")), 12U);
 }
 
-} // namespace
+} // namespace blink