I landed https://codereview.chromium.org/2075463002/#ps20001 and it passed all the trybots but caused the waterfall to fail (c.f.  issue 620552 ).

The reason seems to be is that the trybots didn't even do anything. Analyze determined that nothing needed to be done, despite changing a script referenced in //build/toolchain/mac. There doesn't appear to be a way to have a tool or toolchain take a list of input scripts, so I'm not sure if we fix this in the build system or in analyze.