C bindings: Implement _DeepCopy() & some unittests.

mojom/generators/c/templates/struct.tmpl.go

Index: mojom/generators/c/templates/struct.tmpl.go
diff --git a/mojom/generators/c/templates/struct.tmpl.go b/mojom/generators/c/templates/struct.tmpl.go
index 7cefe7824c66dc78fe74c3fbfdc295b1e72ab203..7ba98bc67acca812f8153e470b64b409813a9ced 100644
--- a/mojom/generators/c/templates/struct.tmpl.go
+++ b/mojom/generators/c/templates/struct.tmpl.go
@@ -38,7 +38,7 @@ void {{$struct.Name}}_CloseAllHandles(
 
 struct {{$struct.Name}}* {{$struct.Name}}_DeepCopy(
   struct MojomBuffer* in_buffer,
-  struct {{$struct.Name}}* in_data);
+  struct {{$struct.Name}}* in_struct);
 
 size_t {{$struct.Name}}_ComputeSerializedSize(
   const struct {{$struct.Name}}* in_data);
@@ -68,6 +68,19 @@ const GenerateStructDefinitions = `
 const {{$const.Type}} {{$const.Name}} = {{$const.Value}};
 {{end -}}
 
+struct {{$struct.Name}}* {{$struct.Name}}_DeepCopy(
+  struct MojomBuffer* in_buffer,
+  struct {{$struct.Name}}* in_struct) {
+  struct {{$struct.Name}}* out_struct = NULL;
+  if (!MojomStruct_DeepCopy(
+      in_buffer, &{{$struct.Name}}__TypeDesc,
+      (struct MojomStructHeader*)in_struct,
+      (struct MojomStructHeader**)&out_struct)) {
+    return NULL;
+  }
+  return out_struct;
+}
+
 size_t {{$struct.Name}}_ComputeSerializedSize(
     const struct {{$struct.Name}}* in_data) {
   return MojomStruct_ComputeSerializedSize(