[tracing] Use locale independent writer for FP values.

test/cctest/test-traced-value.cc

Index: test/cctest/test-traced-value.cc
diff --git a/test/cctest/test-traced-value.cc b/test/cctest/test-traced-value.cc
index 5a8b9ab9c498bf3009d563f8b6f458d9b45275e2..1c3e7ac2522d7e37939ee0861889f5a1dcffb01a 100644
--- a/test/cctest/test-traced-value.cc
+++ b/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);
 }