Add Angle GN build file.

BUG=
R=kbr@chromium.org

Review URL: https://codereview.chromium.org/308673004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@273684 0039d316-1c4b-4281-b951-d872f2087c98

BUILD.gn

@@ -49,6 +49,7 @@ group("root") {
     #"//sdch",
     "//skia",
     "//sql",
+    "//third_party/angle:translator",
     "//third_party/brotli",
     "//third_party/harfbuzz-ng",
     "//third_party/iccjpeg",