Mojo C++ bindings: some improvements for String16 struct traits.

third_party/WebKit/Source/platform/mojo/CommonCustomTypesStructTraits.h

Index: third_party/WebKit/Source/platform/mojo/CommonCustomTypesStructTraits.h
diff --git a/third_party/WebKit/Source/platform/mojo/CommonCustomTypesStructTraits.h b/third_party/WebKit/Source/platform/mojo/CommonCustomTypesStructTraits.h
index 3318ad8fc1eab3d617c7a892bae11eb2d5ab5aeb..40595811d9769a9f7fdece63cdba4895cf9ff7cf 100644
--- a/third_party/WebKit/Source/platform/mojo/CommonCustomTypesStructTraits.h
+++ b/third_party/WebKit/Source/platform/mojo/CommonCustomTypesStructTraits.h
@@ -5,6 +5,7 @@
 #ifndef CommonCustomTypesStructTraits_h
 #define CommonCustomTypesStructTraits_h
 
+#include "base/strings/string16.h"
 #include "mojo/common/common_custom_types.mojom-blink.h"
 #include "platform/PlatformExport.h"
 
@@ -12,9 +13,17 @@ namespace mojo {
 
 template <>
 struct PLATFORM_EXPORT
-    StructTraits<mojo::common::mojom::String16DataView, ::WTF::String> {
-  static WTF::Vector<uint16_t> data(const ::WTF::String&);
-  static bool Read(mojo::common::mojom::String16DataView, ::WTF::String* out);
+    StructTraits<common::mojom::String16DataView, WTF::String> {
+  static bool IsNull(const WTF::String& input) { return input.isNull(); }
+  static void SetToNull(WTF::String* output) { *output = WTF::String(); }
+
+  static void* SetUpContext(const WTF::String& input);
+  static void TearDownContext(const WTF::String& input, void* context) {
+    delete static_cast<base::string16*>(context);
+  }
+
+  static ConstCArray<uint16_t> data(const WTF::String& input, void* context);
+  static bool Read(common::mojom::String16DataView, WTF::String* out);
 };
 
 }  // namespace mojo