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

ui/events/latency_info.cc

Index: ui/events/latency_info.cc
diff --git a/ui/events/latency_info.cc b/ui/events/latency_info.cc
index 96fe74c166c96f206ee6d55d7cd6040bc241c0d4..597b80de2bfe9b6fbbd4f30d13778e9d69c63f42 100644
--- a/ui/events/latency_info.cc
+++ b/ui/events/latency_info.cc
@@ -108,7 +108,7 @@ LatencyInfoTracedValue::~LatencyInfoTracedValue() {
 
 void LatencyInfoTracedValue::AppendAsTraceFormat(std::string* out) const {
   std::string tmp;
-  base::JSONWriter::Write(value_.get(), &tmp);
+  base::JSONWriter::Write(*value_, &tmp);
   *out += tmp;
 }