Mipmapping for ImageLayers was enabled with:
However, it turns out that a lot of regular HTML content makes no use of mipmap levels since images are drawn untransformed and in their source resolution. In addition, mipmaping seems to have tickled an ANGLE bug:
A possible alternative solution once the ANGLE bug is resolved would be to turn on mipmapping only for layers that are displayed at a smaller size that would make effective use of the gpu.
Created attachment 71187 [details]
Comment on attachment 71187 [details]
Verified that this patch is a reversion of the earlier one.
Committed r70075: <http://trac.webkit.org/changeset/70075>