Bug 125133

Summary: [Coordinated Graphics] An element with background-size:cover is drawn incorrectly under certain condition.
Product: WebKit Reporter: Jeong Jin Gyeong <jjgjoojis>
Component: Layout and RenderingAssignee: Nobody <webkit-unassigned>
Status: NEW ---    
Severity: Normal CC: dtrebbien, jaepark, nick.diego, noam, yoon
Priority: P2    
Version: 528+ (Nightly build)   
Hardware: PC   
OS: Linux   
URL: http://black.company100.com/test/background-size-cover/

Description Jeong Jin Gyeong 2013-12-02 22:43:20 PST 
It is appeared in EFL. I checked at r159833.

Test:
  http://black.company100.com/test/background-size-cover/

The color of rightmost pixel is expected to be cyan.
Google Chrome 27 works correctly.
EFL MiniBrowser displays black pixel at rightmost.


I found 2 reappearance conditions.
The gap is appeared if at least one of the conditions is true.

1. Set position style of the element to fixed
  { position: fixed; }
2. Make the element an AC layer.
  { -webkit-transform: translateZ(0); }

The above test applies 2nd condition only. ( position: absolute, -webkit-transform: translateZ(0). )