Enable C++11 features in rapidjson

Change-Id: Ia40c43682cf3b482bc0a425b38b2b3af594d6bbc

BUILD.gn

diff --git a/BUILD.gn b/BUILD.gn
index 8622600..431d0fc 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -29,6 +29,16 @@
   include_dirs = [
     ".",
   ]
+
+  # rapidjson needs these defines to support C++11 features. These features
+  # are intentionally not autodetected by rapidjson.
+  defines = [
+    "RAPIDJSON_HAS_STDSTRING",
+    "RAPIDJSON_HAS_CXX11_RANGE_FOR",
+    "RAPIDJSON_HAS_CXX11_RVALUE_REFS",
+    "RAPIDJSON_HAS_CXX11_TYPETRAITS",
+    "RAPIDJSON_HAS_CXX11_NOEXCEPT",
+  ]
 }
 
 source_set("rapidjson") {