First step to move common accessibility code out of content.

content/public/common/ax_tree.cc

Index: content/public/common/ax_tree.cc
diff --git a/tools/gn/config_values.cc b/content/public/common/ax_tree.cc
similarity index 57%
copy from tools/gn/config_values.cc
copy to content/public/common/ax_tree.cc
index 53466dfd79180b8c211b9d9202a1db73b9166f36..93531af381132fe2f44178290b3e754755f8712c 100644
--- a/tools/gn/config_values.cc
+++ b/content/public/common/ax_tree.cc
@@ -2,10 +2,14 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "tools/gn/config_values.h"
+#include "content/public/common/ax_tree.h"
 
-ConfigValues::ConfigValues() {
+namespace content {
+
+AXTree::AXTree() {
 }
 
-ConfigValues::~ConfigValues() {
+AXTree::~AXTree() {
 }
+
+}  // namespace content