Move BookmarkExpandedStateTracker into bookmarks namespace.

components/bookmarks/browser/bookmark_expanded_state_tracker_unittest.cc

Index: components/bookmarks/browser/bookmark_expanded_state_tracker_unittest.cc
diff --git a/components/bookmarks/browser/bookmark_expanded_state_tracker_unittest.cc b/components/bookmarks/browser/bookmark_expanded_state_tracker_unittest.cc
index 3cbe6e00bb82c248a69534c7d427e2d3168c2d78..e33d4d3985f0176dd2d4e1fe25d5439c8e848f72 100644
--- a/components/bookmarks/browser/bookmark_expanded_state_tracker_unittest.cc
+++ b/components/bookmarks/browser/bookmark_expanded_state_tracker_unittest.cc
@@ -18,6 +18,8 @@
 #include "components/pref_registry/pref_registry_syncable.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+namespace bookmarks {
+
 scoped_ptr<PrefService> PrefServiceForTesting() {
   scoped_refptr<user_prefs::PrefRegistrySyncable> registry(
       new user_prefs::PrefRegistrySyncable());
@@ -110,3 +112,5 @@ TEST_F(BookmarkExpandedStateTrackerTest, RemoveAllUserBookmarks) {
   // Verify node is not present.
   EXPECT_TRUE(tracker->GetExpandedNodes().empty());
 }
+
+}  // namespace bookmarks