[ABANDONED] Make it possible to send unique_ptr<Value> over IPC/Mojo.

ipc/ipc_message_utils.cc

Index: ipc/ipc_message_utils.cc
diff --git a/ipc/ipc_message_utils.cc b/ipc/ipc_message_utils.cc
index 0060f867277aa207fb106a937d292acab0723155..acd147048cbd1f5f4e4163ff0036c2dd4a63c195 100644
--- a/ipc/ipc_message_utils.cc
+++ b/ipc/ipc_message_utils.cc
@@ -9,6 +9,7 @@
 
 #include "base/files/file_path.h"
 #include "base/json/json_writer.h"
+#include "base/memory/ptr_util.h"
 #include "base/strings/nullable_string16.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/utf_string_conversions.h"
@@ -636,6 +637,51 @@ void ParamTraits<base::DictionaryValue>::Log(const param_type& p,
   l->append(json);
 }
 
+void ParamTraits<std::unique_ptr<base::Value>>::GetSize(
+    base::PickleSizer* sizer,
+    const param_type& p) {
+  bool valid = !!p;
+  GetParamSize(sizer, valid);
+  if (valid)
+    GetValueSize(sizer, p.get(), 0);
+}
+
+void ParamTraits<std::unique_ptr<base::Value>>::Write(base::Pickle* m,
+                                                      const param_type& p) {
+  bool valid = !!p;
+  WriteParam(m, valid);
+  if (valid)
+    WriteValue(m, p.get(), 0);
+}
+
+bool ParamTraits<std::unique_ptr<base::Value>>::Read(const base::Pickle* m,
+                                                     base::PickleIterator* iter,
+                                                     param_type* r) {
+  bool valid = false;
+  if (!ReadParam(m, iter, &valid))
+    return false;
+
+  if (!valid) {
+    r->reset();
+    return true;
+  }
+
+  base::Value* temp = nullptr;
+  if (!ReadValue(m, iter, &temp, 0))
+    return false;
+
+  *r = base::WrapUnique(temp);
+  return true;
+}
+
+void ParamTraits<std::unique_ptr<base::Value>>::Log(const param_type& p,
+                                                    std::string* l) {
+  std::string json = "nullptr";

[yzshen1, 2016/11/03 21:59:24]

nit: maybe default to empty and only set "nullptr" when p is null (which should
usually be a minor case)?

+  if (p.get())
+    base::JSONWriter::Write(*p, &json);
+  l->append(json);
+}
+
 #if defined(OS_POSIX)
 void ParamTraits<base::FileDescriptor>::GetSize(base::PickleSizer* sizer,
                                                 const param_type& p) {