Convert JsonWriter::Write to taking a const ref for the in-param

components/policy/core/common/cloud/policy_header_service.cc

Index: components/policy/core/common/cloud/policy_header_service.cc
diff --git a/components/policy/core/common/cloud/policy_header_service.cc b/components/policy/core/common/cloud/policy_header_service.cc
index d0f69808293becc85bbdec49aef0523fe6f15a70..62519c75bb95596eed6deb6c0d5bd10dd885b96b 100644
--- a/components/policy/core/common/cloud/policy_header_service.cc
+++ b/components/policy/core/common/cloud/policy_header_service.cc
@@ -74,7 +74,7 @@ std::string PolicyHeaderService::CreateHeaderValue() {
   // TODO(atwilson): add user_policy_token once the server starts sending it
   // down (http://crbug.com/326799).
   std::string json;
-  base::JSONWriter::Write(&value, &json);
+  base::JSONWriter::Write(value, &json);
   DCHECK(!json.empty());
 
   // Base64-encode the result so we can include it in a header.