[inspector] fix timestamp formatting with non C locales

src/inspector/string-util.h

Index: src/inspector/string-util.h
diff --git a/src/inspector/string-util.h b/src/inspector/string-util.h
index 30137b8b786f9796b2286780a2c89194b66b1a43..0d40ae729fa9cb92e0308d7685313eefe0412234 100644
--- a/src/inspector/string-util.h
+++ b/src/inspector/string-util.h
@@ -28,7 +28,9 @@ class StringUtil {
   static String fromInteger(size_t number) {
     return String::fromInteger(number);
   }
-  static String fromDouble(double number) { return String::fromDouble(number); }
+  static String fromDouble(double number) {
+    return String::fromDoubleForcePointAsSeparator(number);
+  }
   static const size_t kNotFound = String::kNotFound;
   static void builderReserve(StringBuilder& builder, size_t capacity) {
     builder.reserveCapacity(capacity);