Add headers to gn/gni files for all of sky/engine

sky/viewer/cc/BUILD.gn

 # Copyright 2014 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.
 
 component("cc") {
   output_name = "sky_viewer_cc"
 
   deps = [
     "//base",
     "//base/third_party/dynamic_annotations",
@@ skipping 54 matching lines @@
   deps = [
     ":cc",
     "//base/test:run_all_unittests",
     "//base/third_party/dynamic_annotations",
     "//skia",
     "//testing/gtest",
     "//ui/gfx/geometry",
     "//ui/gfx:test_support",
     "//cc",
     "//cc:test_support",
+    "//sky/engine/public:sky_headers",
   ]
 
   sources = [
     "web_animation_unittest.cc",
     "web_float_animation_curve_unittest.cc",
     "web_layer_impl_fixed_bounds_unittest.cc",
   ]
 }