Bug 774689 - Mark 632781-verybig.html fails-if on WinXP for too many intermittent failures
Bug 850181 - Skip conformance/textures/texture-mips.html on Ubuntu VMs since they intermittently pass and fail in equal measure
Backed out changeset 8c37f4a3e488 (bug 874407) for failures in test_bug549192.xul