Add GN buildfile for gfx

Adds libjpeg and some global flags for Ozone from the GYP build.

Improves error messages for mismatched item types I noticed when writing this patch (changes in builder.cc).

BUG=
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Review URL: https://codereview.chromium.org/224633002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@263086 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/BUILD.gn b/BUILD.gn
index 673c865..764805db 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -44,7 +44,7 @@
     "//third_party/zlib",
     "//tools/gn",
     "//ui/events",
-    "//ui/gfx/geometry",
+    "//ui/gfx",
     "//url",
   ]