The context:  https://crbug.com/715034 

I am preparing to land the CL which disables /deep/ (and ::shadow). The CL should be landed for M60.
The WIP CL: https://codereview.chromium.org/2778983006

It looks the following test will fail in according to the try results:
https://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_rel_ng/builds/438296

- TouchActionTest.ShadowDOM

It looks touch-action-tests.css is using /deep/. It needs to be rewritten.
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/web/tests/data/touch-action-tests.css


It looks this CL introduced /deep/ here.
https://codereview.chromium.org/143993006

That's me. :(