Profile performance on image-heavy posts.

Make sure the editing experience is as smooth as possible on image-heavy posts.

Example content:

<img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://static.businessinsider.com/image/57717085dd089531228b4a1f.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://cdn.spacetelescope.org/archives/images/large/heic0807c.jpg"><img src="https://www.nasa.gov/sites/default/files/thumbnails/image/pia21394.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://lambda.gsfc.nasa.gov/product/map/dr5/map_images/9yr_4096/k_9yr_temp_4096.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://static.businessinsider.com/image/57717085dd089531228b4a1f.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://cdn.spacetelescope.org/archives/images/large/heic0807c.jpg"><img src="https://www.nasa.gov/sites/default/files/thumbnails/image/pia21394.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://lambda.gsfc.nasa.gov/product/map/dr5/map_images/9yr_4096/k_9yr_temp_4096.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://static.businessinsider.com/image/57717085dd089531228b4a1f.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://cdn.spacetelescope.org/archives/images/large/heic0807c.jpg"><img src="https://www.nasa.gov/sites/default/files/thumbnails/image/pia21394.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://lambda.gsfc.nasa.gov/product/map/dr5/map_images/9yr_4096/k_9yr_temp_4096.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://static.businessinsider.com/image/57717085dd089531228b4a1f.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://cdn.spacetelescope.org/archives/images/large/heic0807c.jpg"><img src="https://www.nasa.gov/sites/default/files/thumbnails/image/pia21394.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://lambda.gsfc.nasa.gov/product/map/dr5/map_images/9yr_4096/k_9yr_temp_4096.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://static.businessinsider.com/image/57717085dd089531228b4a1f.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://cdn.spacetelescope.org/archives/images/large/heic0807c.jpg"><img src="https://www.nasa.gov/sites/default/files/thumbnails/image/pia21394.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://lambda.gsfc.nasa.gov/product/map/dr5/map_images/9yr_4096/k_9yr_temp_4096.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://static.businessinsider.com/image/57717085dd089531228b4a1f.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://cdn.spacetelescope.org/archives/images/large/heic0807c.jpg"><img src="https://www.nasa.gov/sites/default/files/thumbnails/image/pia21394.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://lambda.gsfc.nasa.gov/product/map/dr5/map_images/9yr_4096/k_9yr_temp_4096.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://static.businessinsider.com/image/57717085dd089531228b4a1f.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://cdn.spacetelescope.org/archives/images/large/heic0807c.jpg"><img src="https://www.nasa.gov/sites/default/files/thumbnails/image/pia21394.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://lambda.gsfc.nasa.gov/product/map/dr5/map_images/9yr_4096/k_9yr_temp_4096.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://static.businessinsider.com/image/57717085dd089531228b4a1f.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://cdn.spacetelescope.org/archives/images/large/heic0807c.jpg"><img src="https://www.nasa.gov/sites/default/files/thumbnails/image/pia21394.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://lambda.gsfc.nasa.gov/product/map/dr5/map_images/9yr_4096/k_9yr_temp_4096.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://static.businessinsider.com/image/57717085dd089531228b4a1f.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://cdn.spacetelescope.org/archives/images/large/heic0807c.jpg"><img src="https://www.nasa.gov/sites/default/files/thumbnails/image/pia21394.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://lambda.gsfc.nasa.gov/product/map/dr5/map_images/9yr_4096/k_9yr_temp_4096.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://static.businessinsider.com/image/57717085dd089531228b4a1f.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://cdn.spacetelescope.org/archives/images/large/heic0807c.jpg"><img src="https://www.nasa.gov/sites/default/files/thumbnails/image/pia21394.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://lambda.gsfc.nasa.gov/product/map/dr5/map_images/9yr_4096/k_9yr_temp_4096.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://static.businessinsider.com/image/57717085dd089531228b4a1f.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://cdn.spacetelescope.org/archives/images/large/heic0807c.jpg"><img src="https://www.nasa.gov/sites/default/files/thumbnails/image/pia21394.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://lambda.gsfc.nasa.gov/product/map/dr5/map_images/9yr_4096/k_9yr_temp_4096.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://static.businessinsider.com/image/57717085dd089531228b4a1f.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://cdn.spacetelescope.org/archives/images/large/heic0807c.jpg"><img src="https://www.nasa.gov/sites/default/files/thumbnails/image/pia21394.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://lambda.gsfc.nasa.gov/product/map/dr5/map_images/9yr_4096/k_9yr_temp_4096.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://static.businessinsider.com/image/57717085dd089531228b4a1f.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://cdn.spacetelescope.org/archives/images/large/heic0807c.jpg"><img src="https://www.nasa.gov/sites/default/files/thumbnails/image/pia21394.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://lambda.gsfc.nasa.gov/product/map/dr5/map_images/9yr_4096/k_9yr_temp_4096.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://static.businessinsider.com/image/57717085dd089531228b4a1f.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://cdn.spacetelescope.org/archives/images/large/heic0807c.jpg"><img src="https://www.nasa.gov/sites/default/files/thumbnails/image/pia21394.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://lambda.gsfc.nasa.gov/product/map/dr5/map_images/9yr_4096/k_9yr_temp_4096.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://static.businessinsider.com/image/57717085dd089531228b4a1f.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://cdn.spacetelescope.org/archives/images/large/heic0807c.jpg"><img src="https://www.nasa.gov/sites/default/files/thumbnails/image/pia21394.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://lambda.gsfc.nasa.gov/product/map/dr5/map_images/9yr_4096/k_9yr_temp_4096.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://upload.wikimedia.org/wikipedia/commons/6/64/Durdle_Door_Overview.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://static.businessinsider.com/image/57717085dd089531228b4a1f.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://cdn.spacetelescope.org/archives/images/large/heic0807c.jpg"><img src="https://www.nasa.gov/sites/default/files/thumbnails/image/pia21394.jpg"><img src="https://examplebloge.files.wordpress.com/2017/02/3def4804-d9b5-11e6-88e6-d7d8864392e0.png"><img src="https://lambda.gsfc.nasa.gov/product/map/dr5/map_images/9yr_4096/k_9yr_temp_4096.png">

Use the issue's HTML example with repeated external images to reproduce the editing experience in the iOS editor and profile where responsiveness degrades. No source file, test, profiling entry point, or completion threshold is named, so identify the relevant path and establish a measurable baseline before determining what improvement counts as done.