third_party/blink/web_tests/images/content-url-image-with-alt-text-dynamic-2.html - chromium/src - Git at Google

 <!DOCTYPE html>
 <style>
 #img {content:url('resources/lenna.png')}
 </style>
 <img id='img' alt='test image'>
 <script>
     document.getElementById('img').style.content = "url('ImageDoesNotExist')";
     document.getElementById('img').style.content = "url('resources/lenna.png')";
     document.getElementById('img').style.content = "url('ImageDoesNotExist')";
 </script>
 <p>crbug.com/516239: images set by content: url() should behave correctly with alt text.
	<!DOCTYPE html>
	<style>
	#img {content:url('resources/lenna.png')}
	</style>
	<img id='img' alt='test image'>
	<script>
	document.getElementById('img').style.content = "url('ImageDoesNotExist')";
	document.getElementById('img').style.content = "url('resources/lenna.png')";
	document.getElementById('img').style.content = "url('ImageDoesNotExist')";
	</script>
	<p>crbug.com/516239: images set by content: url() should behave correctly with alt text.