fast/.../frameset-repeated-name.html in webkit_layout_tests failing on chromium.webkit/WebKit Win10

Builders failed on: 
- WebKit Win10: 
  https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Win10


It seems like there's a racing condition here:
Sometimes 
(file test):fast/history/resources/frameset-dest.html (in frame "<!--framePath //<!--frame0-->-->")
                about:blank (in frame "f1")
                about:blank (in frame "f2")
                about:blank (in frame "f3")
                about:blank (in frame "f4")
occurs first, but some other times
(file test):fast/history/resources/frameset-dest.html (in frame "<!--framePath //<!--frame1-->-->")
                about:blank (in frame "<!--framePath //<!--frame1-->/<!--frame0-->-->")
                about:blank (in frame "<!--framePath //<!--frame1-->/<!--frame1-->-->")
                about:blank (in frame "<!--framePath //<!--frame1-->/<!--frame2-->-->")
                about:blank (in frame "<!--framePath //<!--frame1-->/<!--frame3-->-->")
===============================================
occurs first.

I will mark it as flaky for now, dcheng@ please help take a look.