[tracing] Use locale independent writer for FP values.

src/tracing/traced-value.cc

Index: src/tracing/traced-value.cc
diff --git a/src/tracing/traced-value.cc b/src/tracing/traced-value.cc
index 58d0f5d5bac9dfb016697e62032cc3d6003b6dd1..9b2a45c99107096a9a7d7f858d7f06e5f8038187 100644
--- a/src/tracing/traced-value.cc
+++ b/src/tracing/traced-value.cc
@@ -5,6 +5,7 @@
 #include "src/tracing/traced-value.h"
 
 #include "src/base/platform/platform.h"
+#include "src/conversions.h"
 
 namespace v8 {
 namespace tracing {
@@ -80,7 +81,8 @@ void TracedValue::SetInteger(const char* name, int value) {
 void TracedValue::SetDouble(const char* name, double value) {
   DCHECK_CURRENT_CONTAINER_IS(kStackTypeDict);
   WriteName(name);
-  data_ += std::to_string(value);
+  i::EmbeddedVector<char, 100> buffer;
+  data_ += DoubleToCString(value, buffer);
 }
 
 void TracedValue::SetBoolean(const char* name, bool value) {
@@ -120,7 +122,8 @@ void TracedValue::AppendInteger(int value) {
 void TracedValue::AppendDouble(double value) {
   DCHECK_CURRENT_CONTAINER_IS(kStackTypeArray);
   WriteComma();
-  data_ += std::to_string(value);
+  i::EmbeddedVector<char, 100> buffer;
+  data_ += DoubleToCString(value, buffer);
 }
 
 void TracedValue::AppendBoolean(bool value) {