Make TracedValue lower overhead.

base/json/json_writer.cc

Index: base/json/json_writer.cc
diff --git a/base/json/json_writer.cc b/base/json/json_writer.cc
index 6a9cc6aa470b592e6a76919236fe71706fd93036..3521698917dc2b56924f872484a1bee6f7a07244 100644
--- a/base/json/json_writer.cc
+++ b/base/json/json_writer.cc
@@ -50,6 +50,34 @@ void JSONWriter::WriteWithOptions(const Value* const node, int options,
     json->append(kPrettyPrintLineEnding);
 }
 
+std::string JSONWriter::DoubleToFormattedString(double value,
+    bool omit_double_type_preservation) {
+  if (omit_double_type_preservation &&
+      value <= kint64max &&
+      value >= kint64min &&
+      std::floor(value) == value) {
+    return Int64ToString(static_cast<int64>(value));
+  }
+  std::string real = DoubleToString(value);
+  // Ensure that the number has a .0 if there's no decimal or 'e'.  This
+  // makes sure that when we read the JSON back, it's interpreted as a
+  // real rather than an int.
+  if (real.find('.') == std::string::npos &&
+      real.find('e') == std::string::npos &&
+      real.find('E') == std::string::npos) {
+    real.append(".0");
+  }
+  // The JSON spec requires that non-integer values in the range (-1,1)
+  // have a zero before the decimal point - ".52" is not valid, "0.52" is.
+  if (real[0] == '.') {
+    real.insert(0, "0");
+  } else if (real.length() > 1 && real[0] == '-' && real[1] == '.') {
+    // "-.1" bad "-0.1" good
+    real.insert(1, "0");
+  }
+  return real;
+}
+
 JSONWriter::JSONWriter(bool escape, bool omit_binary_values,
                        bool omit_double_type_preservation, bool pretty_print,
                        std::string* json)
@@ -90,31 +118,8 @@ void JSONWriter::BuildJSONString(const Value* const node, int depth) {
         double value;
         bool result = node->GetAsDouble(&value);
         DCHECK(result);
-        if (omit_double_type_preservation_ &&
-            value <= kint64max &&
-            value >= kint64min &&
-            std::floor(value) == value) {
-          json_string_->append(Int64ToString(static_cast<int64>(value)));
-          break;
-        }
-        std::string real = DoubleToString(value);
-        // Ensure that the number has a .0 if there's no decimal or 'e'.  This
-        // makes sure that when we read the JSON back, it's interpreted as a
-        // real rather than an int.
-        if (real.find('.') == std::string::npos &&
-            real.find('e') == std::string::npos &&
-            real.find('E') == std::string::npos) {
-          real.append(".0");
-        }
-        // The JSON spec requires that non-integer values in the range (-1,1)
-        // have a zero before the decimal point - ".52" is not valid, "0.52" is.
-        if (real[0] == '.') {
-          real.insert(0, "0");
-        } else if (real.length() > 1 && real[0] == '-' && real[1] == '.') {
-          // "-.1" bad "-0.1" good
-          real.insert(1, "0");
-        }
-        json_string_->append(real);
+        json_string_->append(DoubleToFormattedString(value,
+            omit_double_type_preservation_));
         break;
       }