Version: 54.0.2798.0
OS: macOS 10.11

What steps will reproduce the problem?
(1) Go to, for example, https://www.youtube.com/watch?v=NrjneJvS6dk
(2) Move the mouse around the page, over the sections that are not displaying a movie

Portions of the page are white, as if they have been marked for update but have not been redrawn. It seems to be related to regions that reveal something or redraw when you mouse over them. For example, the second screenshot was taken after moving the mouse down and landing over a link. The link was redrawn but there's a big white space all around. 

Regression range is 54.0.2795.0::54.0.2798.0.

https://chromium.googlesource.com/chromium/src/+log/54.0.2795.0..54.0.2798.0?pretty=fuller&n=10000

Does not happen on Windows. The problem goes away if I disable GPU Raster.
 

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	Screen Shot 2016-07-20 at 2.35.46 PM.png 496 KB View Download