Add Widevine signature files into Mac build

third_party/widevine/cdm/widevine.gni

Index: third_party/widevine/cdm/widevine.gni
diff --git a/third_party/widevine/cdm/widevine.gni b/third_party/widevine/cdm/widevine.gni
index b10a92b47494fe4954df89e40b9e4e80a12fb653..fb92dd41494fd34a4c79e0d654413a229474fc2b 100644
--- a/third_party/widevine/cdm/widevine.gni
+++ b/third_party/widevine/cdm/widevine.gni
@@ -6,3 +6,26 @@ declare_args() {
   # Allow widevinecdmadapter to be built in Chromium.
   enable_widevine = false
 }
+
+template("widevine_sign_file") {

[xhwang, 2017/01/28 05:21:53]

Please add a comment about what this template is doing.

[jrummell, 2017/01/31 22:29:18]

Done.

+  action(target_name) {
+    forward_variables_from(invoker,
+                           [
+                             "file",
+                             "deps",

[xhwang, 2017/01/28 05:21:53]

Is "deps" needed? Seems not used in this template.

[jrummell, 2017/01/31 22:29:18]

We need the generated action to have a deps so it gets built in the correct
order.

+                           ])
+    script = "//third_party/widevine/scripts/signature_generator.py"
+    sources = [
+      "$file",
+    ]
+    outputs = [
+      "$file.sig",
+    ]
+    args = [
+      "--input_file",
+      rebase_path("$file", root_build_dir),
+      "--output_file",
+      rebase_path("$file.sig", root_build_dir),
+    ]
+  }
+}