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

Source/core/dom/TreeScopeTest.cpp

Index: Source/core/dom/TreeScopeTest.cpp
diff --git a/Source/core/dom/TreeScopeTest.cpp b/Source/core/dom/TreeScopeTest.cpp
index f31d149f05177c913e9ba6b00eb98d1ffd110f79..aa8a48ef44c67f331a0267409da3a17e3f0f1cac 100644
--- a/Source/core/dom/TreeScopeTest.cpp
+++ b/Source/core/dom/TreeScopeTest.cpp
@@ -10,9 +10,7 @@
 #include "core/dom/shadow/ShadowRoot.h"
 #include <gtest/gtest.h>
 
-using namespace blink;
-
-namespace {
+namespace blink {
 
 TEST(TreeScopeTest, CommonAncestorOfSameTrees)
 {
@@ -96,4 +94,4 @@ TEST(TreeScopeTest, CommonAncestorOfTreesInDifferentDocuments)
     EXPECT_EQ(0, document2->commonAncestorTreeScope(*document1));
 }
 
-} // namespace
+} // namespace blink