We should able to support box shadows with a uniform border radius in WR.

This patch allows nsDisplayBoxShadowInner to render uniform radius via WebRender. Some reftests are needed to be fuzzed due to the following reasons: 1. boxshadow-border-radius-int.html : There are a little differences between inner shadow between the cases that with and without border radius which is rendered by WebRender. 2. fieldset-inset.html : nsDisplayFieldSetBorder for WebRender is not supported in gecko; therefore, before the implementation is completed, this test will be a comparison between old compositor and WebRender.

Comment on attachment 8904397 [details] Bug 1396492 - Support uniform radius for nsDisplayBoxShadowInner; https://reviewboard.mozilla.org/r/176204/#review181872

I will land this patch after 9/21 since the soft freeze.

Since this only touches CanCreateWebRenderCommands the likeliness of it causes regression should be really low. You shouldn't have to wait for 9/21.

Here is the try result[1], this patch should only affect QuantumRender build; the failures in other builds are not related to this patch. [1] https://treeherder.mozilla.org/#/jobs?repo=try&revision=cdfba1e072fe7ed9f9ddf9bb314393306eb350d4