Add FontFaceSource interface and make it available on Document

third_party/WebKit/Source/core/css/FontFaceSource.cpp

Index: third_party/WebKit/Source/core/css/FontFaceSource.cpp
diff --git a/third_party/WebKit/Source/core/css/FontFaceSource.cpp b/third_party/WebKit/Source/core/css/FontFaceSource.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..4d4dc4ab75f0cbbd951df62da0d1ea4bab644a4f
--- /dev/null
+++ b/third_party/WebKit/Source/core/css/FontFaceSource.cpp
@@ -0,0 +1,15 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/css/FontFaceSource.h"
+
+#include "core/css/FontFaceSet.h"
+
+namespace blink {
+
+FontFaceSet* FontFaceSource::fonts(Document& document) {
+  return FontFaceSet::From(document);
+}
+
+}  // namespace blink