Bug 168482

Summary: Very slow composite (~300ms) when rendering images over 6K px in width
Product: WebKit Reporter: Yuriy Nemtsov <nemtsov>
Component: ImagesAssignee: Nobody <webkit-unassigned>
Status: NEW ---    
Severity: Major CC: mike.sherov, sabouhallawa, simon.fraser
Priority: P2    
Version: Safari 10   
Hardware: Mac   
OS: OS X 10.11   

Description Yuriy Nemtsov 2017-02-16 16:29:42 PST 
When adding (16 in the test below) images that have a width and height of 6k px, and then scrolling the container, the scroll will be very laggy. Timelines show that Composite duration was about 300ms.

The issue can be seen in the following jsFiddle:
https://jsfiddle.net/nemtsov/ad8a5ugz/