Closing Writable is Slow If Content Contains Certain Character Sequence

Saving file content with certain character sequence such as <htmlscript> is twice as slow than without.

async function writeFile(fileHandle, contents) {
  const writable = await fileHandle.createWritable();
  await writable.write('<htmlscript>'); // 2-3x times slower than without when closing

  let then = new Date();

  await writable.close();

  let now = new Date();

  let elapsed = new Date(now - then).getTime();
  console.log(elapsed);
}

Test cases ;

htmlscript : fast
<htmlscript> : slow
<html Whatever Character Between script> : slow
html Whatever Character Between script : fast
for example <if html script> slow> : fast
for example if< html script> slow> : slow
for example <if html script> slow> < html > : slow
for example <if html script> slow> < script > : fast
for example script> <html> : slow
for example <html> <script : fast
for example <html> script> : slow

Tested on blank project as well as File System Access API demo : https://googlechromelabs.github.io/text-editor/.

Tested on OS :

Win 10, Chrome 120 : issue persist
ChromeOS 119 : no issue

Changing the MIME type on file picker options also has no effect on this issue :

async function getNewFileHandle() {
  const options = {
    /*
    types: [
      {
        description: 'Text Files',
        accept: {
          'text/html': ['.html'],
        },
      },
    ],
    // */
  };
  let handle = await window.showSaveFilePicker(options);
  return handle;
}

WICG / file-system-access

Closing Writable is Slow If Content Contains Certain Character Sequence #434