Move libxml_utils from chrome/common to third_party/libxml/chromium.

chrome/test/DEPS

 include_rules = [
   # The test directory can do whatever it wants in chrome.
   "+chrome",
 
   # Tests under chrome/ shouldn't need to access the internals of
   # content/ and as such are allowed only content/public and
   # content/test (which is the "public" directory for tests depending
   # on content/).  If you find yourself wanting to write such a test,
   # or a test that depends primarily on content, think about whether
   # the test belongs under content/, or should be split up into a test
   # within content/ and a test within chrome/.
   "-content",
   "+content/public",
   "+content/test",
 
   # TODO(joi): Need to remove all of these and use only content/public
   # and content/test. http://crbug.com/98716
   # DO NOT ADD ANY MORE ITEMS TO THE LIST BELOW!
   "+content/browser/net/url_request_mock_http_job.h",
   "+content/browser/net/url_request_slow_http_job.h",
   "+content/browser/trace_controller.h",
   "+content/common/debug_flags.h",
   "+content/common/injection_test_dll.h",
   "+content/renderer/mock_content_renderer_client.h",
   # DO NOT ADD ANY MORE ITEMS TO THE ABOVE LIST!
 
   "+grit",  # For generated headers
+  "+libxml",  # For parsing the init and output files for automated_ui_tests.
   "+sandbox/src",
   "+sandbox/tests",
   "+webkit/glue",
   "+webkit/plugins",
 ]