[GN build] Add a BUILD.gn file for //third_party/decklink

third_party/decklink/BUILD.gn

Index: third_party/decklink/BUILD.gn
diff --git a/device/core/BUILD.gn b/third_party/decklink/BUILD.gn
similarity index 58%
copy from device/core/BUILD.gn
copy to third_party/decklink/BUILD.gn
index 7d1671fafe0591258ea6b68544150f672debebc0..f9a01b28d99a5dc1bc3d014a9f1b48e0f6e67796 100644
--- a/device/core/BUILD.gn
+++ b/third_party/decklink/BUILD.gn
@@ -2,9 +2,10 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-source_set("core") {
-  sources = [
-    "device_client.cc",
-    "device_client.h",
-  ]
+if (is_mac) {
+  static_library("decklink") {

[jamesr, 2014/09/23 04:08:18]

can you please add a reference to the gyp equivalent and a backref for gyp? i.e.
something like

# GYP version: third_party/decklink/decklink.gyp:decklink

and in the gyp file

# GN version: //third_party/decklink

it's pretty obvious for trivial cases like this but the markers are useful for
figuring out what's been converted and what to call the target in different
build systems.

+    sources = [
+      "mac/include/DeckLinkAPIDispatch.cpp",
+    ]
+  }
 }