Sketch new SkyView interface to the engine

sky/engine/public/sky/BUILD.gn

+# Copyright 2015 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.
+
+source_set("sky") {
+  deps = [
+    "//skia",
+    "//sky/engine/core",
+    "//sky/engine/platform",
+  ]
+
+  configs += [
+    "//sky/engine:config",
+    "//sky/engine:inside_blink",
+    "//sky/engine:non_test_config",
+  ]
+
+  sources = [
+    "sky_display_metrics.h",
+    "sky_view.cc",
+    "sky_view.h",
+  ]
+}