GitLab

Reviewed by Lars Knoll.

Previously this target ended up generating a file named
Makefile.DerivedSources.DerivedSources, and so on.

* DerivedSources.pro:

git-svn-id: svn://svn.chromium.org/blink/trunk@54412 bbb929c8-8fbe-4397-9dbb-9b2b20218538