Mojo C++ bindings: add StringTraits and ArrayTraits for STL types.

mojo/public/cpp/bindings/tests/struct_with_traits_impl_traits.h

Index: mojo/public/cpp/bindings/tests/struct_with_traits_impl_traits.h
diff --git a/mojo/public/cpp/bindings/tests/struct_with_traits_impl_traits.h b/mojo/public/cpp/bindings/tests/struct_with_traits_impl_traits.h
index 0cfc5e7a520fe76c7127ee00aa9b26f0f1c8bc77..a48430ee7a31d5375a0e1d3da2aea200e31af33d 100644
--- a/mojo/public/cpp/bindings/tests/struct_with_traits_impl_traits.h
+++ b/mojo/public/cpp/bindings/tests/struct_with_traits_impl_traits.h
@@ -8,6 +8,7 @@
 #include <stdint.h>
 
 #include <string>
+#include <vector>
 
 #include "base/strings/string_piece.h"
 #include "mojo/public/cpp/bindings/struct_traits.h"
@@ -17,6 +18,16 @@
 namespace mojo {
 
 template <>
+struct StructTraits<test::StructWithTraitsElement,
+                    test::StructWithTraitsElementImpl> {
+  static bool Read(test::StructWithTraitsElementDataView data,
+                   test::StructWithTraitsElementImpl* output);
+  static int32_t value(const test::StructWithTraitsElementImpl& input) {
+    return input.value;
+  }
+};
+
+template <>
 struct StructTraits<test::StructWithTraits, test::StructWithTraitsImpl> {
   // Deserialization to test::StructTraitsImpl.
   static bool Read(test::StructWithTraitsDataView data,
@@ -37,12 +48,27 @@ struct StructTraits<test::StructWithTraits, test::StructWithTraitsImpl> {
   }
 
   static base::StringPiece f_string(const test::StructWithTraitsImpl& value) {
-    return value.get_string();
+    return value.get_string_as_string_piece();
   }
 
-  static base::StringPiece f_string2(const test::StructWithTraitsImpl& value) {
+  static const std::string& f_string2(const test::StructWithTraitsImpl& value) {
     return value.get_string();
   }
+
+  static const std::vector<std::string>& f_array_string(
+      const test::StructWithTraitsImpl& value) {
+    return value.get_array_string();
+  }
+
+  static const test::StructWithTraitsElementImpl& f_element(
+      const test::StructWithTraitsImpl& value) {
+    return value.get_element();
+  }
+
+  static const std::vector<test::StructWithTraitsElementImpl>& f_array_element(
+      const test::StructWithTraitsImpl& value) {
+    return value.get_array_element();
+  }
 };
 
 }  // namespace mojo