[tracing] Use locale independent writer for FP values.

BUG=5820
LOG=N

Review-Url: https://codereview.chromium.org/2628463002
Cr-Commit-Position: refs/heads/master@{#42256}

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) {

test/cctest/test-traced-value.cc

@@ -16,7 +16,7 @@ TEST(FlatDictionary) {
   std::string json = "PREFIX";
   value->AppendAsTraceFormat(&json);
   CHECK_EQ(
-      "PREFIX{\"int\":2014,\"double\":0.000000,\"bool\":true,\"string\":"
+      "PREFIX{\"int\":2014,\"double\":0,\"bool\":true,\"string\":"
       "\"string\"}",
       json);
 }
@@ -24,13 +24,13 @@ TEST(FlatDictionary) {
 TEST(NoDotPathExpansion) {
   auto value = TracedValue::Create();
   value->SetInteger("in.t", 2014);
-  value->SetDouble("doub.le", 0.0);
+  value->SetDouble("doub.le", -20.25);
   value->SetBoolean("bo.ol", true);
   value->SetString("str.ing", "str.ing");
   std::string json;
   value->AppendAsTraceFormat(&json);
   CHECK_EQ(
-      "{\"in.t\":2014,\"doub.le\":0.000000,\"bo.ol\":true,\"str.ing\":\"str."
+      "{\"in.t\":2014,\"doub.le\":-20.25,\"bo.ol\":true,\"str.ing\":\"str."
       "ing\"}",
       json);
 }
@@ -46,6 +46,7 @@ TEST(Hierarchy) {
   value->SetString("s1", "foo");
   value->EndDictionary();
   value->SetDouble("d0", 0.0);
+  value->SetDouble("d1", 10.5);
   value->SetBoolean("b0", true);
   value->BeginArray("a1");
   value->AppendInteger(1);
@@ -69,8 +70,8 @@ TEST(Hierarchy) {
   value->AppendAsTraceFormat(&json);
   CHECK_EQ(
       "{\"i0\":2014,\"dict1\":{\"i1\":2014,\"dict2\":{\"b2\":false},"
-      "\"s1\":\"foo\"},\"d0\":0.000000,\"b0\":true,\"a1\":[1,true,{\"i2\":3}],"
-      "\"s0\":\"foo\",\"arr1\":[{},[],{}]}",
+      "\"s1\":\"foo\"},\"d0\":0,\"d1\":10.5,\"b0\":true,\"a1\":[1,true,{\"i2\":"
+      "3}],\"s0\":\"foo\",\"arr1\":[{},[],{}]}",
       json);
 }