This is related to bug 52611. The shadow color alpha must be multiplied by the context pen alpha. Fixing this results in correct behavior for Canvas path stroke() and strokeRect() [which relies on stroke()].
Created attachment 79402 [details] Patch
Comment on attachment 79402 [details] Patch r=me, let's hope nobody else chokes on the test :)
The commit-queue encountered the following flaky tests while processing attachment 79402 [details]: fast/spatial-navigation/snav-iframe-flattening-simple.html bug 52783 (author: tonikitoo@webkit.org) The commit-queue is continuing to process your patch.
Comment on attachment 79402 [details] Patch Clearing flags on attachment: 79402 Committed r76206: <http://trac.webkit.org/changeset/76206>
All reviewed patches have been landed. Closing bug.