Move build_config.h from chromium/base/build to chromium/base

Moved build_config.h to mimic the include path on ChromeOS and Brillo.
On those platform, this file is included as just "build/build_config.h"

Change-Id: Ia8a30299cc7f485b38eeeddef2e5210644b3d2a3
Reviewed-on: https://weave-review.googlesource.com/1811
Reviewed-by: Vitaly Buka <vitalybuka@google.com>
diff --git a/third_party/chromium/base/json/json_reader_unittest.cc b/third_party/chromium/base/json/json_reader_unittest.cc
index a5f2530..35becef 100644
--- a/third_party/chromium/base/json/json_reader_unittest.cc
+++ b/third_party/chromium/base/json/json_reader_unittest.cc
@@ -6,12 +6,12 @@
 
 #include <gtest/gtest.h>
 
-#include "base/build/build_config.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/utf_string_conversion_utils.h"
 #include "base/values.h"
+#include "build/build_config.h"
 
 namespace base {