Add first imported w3c test suites for html-elements and shadow-dom.

This is the first pass at importing and running tests from the W3C
using something resembling the long-term process. For now we'll just
try two small sets of tests. We get some failures, so we'll suppress
them using the new test_expectations_w3c.txt file until the failures
can be merged into LayoutTests/TestExpectations upstream.

R=eseidel@chromium.org, abarth@chromium.org, jamesr@chromium.org
BUG=242329

Review URL: https://codereview.chromium.org/100123005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242215 0039d316-1c4b-4281-b951-d872f2087c98
Update .DEPS.git

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242216 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242216