Thanks skobes@. I raised my question here https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/7g2IKzKNc-A.

When click "view" links of deleted document.title-05-expected.txt,  will get "Bad content. Try to upload again". 
Also tried rebase and "upload with --similarity=100 --no-find-copies", still got same error.

Detailed link:
https://codereview.chromium.org/2469983007/diff/60001/third_party/WebKit/LayoutTests/imported/wpt/html/dom/documents/dom-tree-accessors/document.title-05-expected.txt

I found similarity issues like this, I didn't know what's happened:
https://codereview.chromium.org/742293002#msg6(Zhang Lei fixed this)
https://codereview.chromium.org/1887233004/#ps90001(Elliot Glaysher not fix
this)
https://codereview.chromium.org/27220005

Please see https://polygerrit.appspot.com

This is unlikely to be looked at due to the transition happening soon.

Closing in bulk due to Rietveld’s deprecation in favor of Gerrit. If you feel this bug should not have been closed, please feel free to re-open.