Remove dependency on webkit_strings from webkit_unit_tests.
Remove dependency on webkit_strings from webkit_unit_tests.

To test this, it was run the following command lines:

$ rm -rf out/Debug
$ ./build/gyp_chromium
$ ninja -C out/Debug webkit_unit_tests
$ out/Debug/webkit_unit_tests

BUG=338338
TEST=see above
R=abarth@chromium.org

Review URL: https://codereview.chromium.org/382113003

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@177964 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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