Issue 4125 - [emscripten] Convert filter classes to C++

compiled/CommentFilter.cpp

+#include "CommentFilter.h"
+
+CommentFilter::CommentFilter(const String& text)
+    : Filter(text)
+{
+}
+
+Filter::Type CommentFilter::Parse(const String& text)
+{
+  if (text.length() && text[0] == u'!')
+    return Type::COMMENT;
+  else
+    return Type::UNKNOWN;
+}
+
+CommentFilter* CommentFilter::Create(const String& text)
+{
+  Type type = Parse(text);
+  if (type == Type::COMMENT)
+    return new CommentFilter(text);
+  else
+    return nullptr;
+}
+
+Filter::Type CommentFilter::GetType() const
+{
+  return Type::COMMENT;
+}