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

Source/core/editing/SurroundingTextTest.cpp

Index: Source/core/editing/SurroundingTextTest.cpp
diff --git a/Source/core/editing/SurroundingTextTest.cpp b/Source/core/editing/SurroundingTextTest.cpp
index 8804e7758550e3e3ce1251fbac716fa03e2343b9..2c59a8c9ccc9dfc15a86876ff487603a1d8191b7 100644
--- a/Source/core/editing/SurroundingTextTest.cpp
+++ b/Source/core/editing/SurroundingTextTest.cpp
@@ -14,9 +14,7 @@
 #include "core/testing/DummyPageHolder.h"
 #include <gtest/gtest.h>
 
-using namespace blink;
-
-namespace {
+namespace blink {
 
 class SurroundingTextTest : public ::testing::Test {
 protected:
@@ -26,7 +24,7 @@ protected:
     VisibleSelection select(int start, int end);
 
 private:
-    virtual void SetUp() override;
+    void SetUp() override;
 
     OwnPtr<DummyPageHolder> m_dummyPageHolder;
 };
@@ -262,4 +260,4 @@ TEST_F(SurroundingTextTest, TreeRangeSelection)
     }
 }
 
-} // anonymous namespace
+} // namespace blink