REGRESSION (Yosemite): Embedded WebView flickers position: fixed elements during rapid scrolling events

• Component: Layout and Rendering
• Status: NEW ---

[Michael]

Created attachment 240063 [details]
Video demonstrating the bug

Using an embedded WebView inside of an application using the WebKit framework produces 
flickering of position: fixed elements while rapidly scrolling the page. This behavior 
did not exist until OS X Yosemite, Developer Preview #5 — it is believed to be a result 
of: https://bugs.webkit.org/show_bug.cgi?id=135135

Steps to Reproduce:
1. Create an application with an embedded WebView that uses the version 1 of the WebKit 
   provided WebView infrastructure. Not WKWebView. Normal WebView.
2. Load an HTML page with contains a position: fixed element
3. Scroll rapidly to produce flickering behavior

Expected Results:
The expected result is that the element stays statically fixed with no flickering during 
scrolling events

Actual Results:
position: fixed HTML elements flicker during rapid scrolling events

Build Date & Platform:
First seen: OS X Yosemite, Developer Preview #5
Last tested: Intel Mac OS X 10.10, AppleWebKit/600.1.25

Notes:
This bug report is a copy of: <rdar://problem/18211024>

[Michael]

Created attachment 240064 [details]
Sample HTML page

[Simon Fraser (smfr)]

A workaround for this bug is to make the WebView layer-backed.

[Scott Kyle]

Created attachment 245955 [details]
Reduction

This is still an issue on OS X 10.10.2. The attached reduction has a layer-backed WebView that exhibits this bug when scrolling back and forth NYTimes. You can enter `https://www.facebook.com` to see it very prominently there when scrolling up and down as well. This has resulted in many negative reviews for my app.