[Mac/GN] Set up the component build.

media/base/mac/BUILD.gn

Index: media/base/mac/BUILD.gn
diff --git a/media/base/mac/BUILD.gn b/media/base/mac/BUILD.gn
index 95540d6890ff462f3ff4911308669a0e501a5a35..b5ac5551fdcdaba4c9694d4d50810c05ed485c48 100644
--- a/media/base/mac/BUILD.gn
+++ b/media/base/mac/BUILD.gn
@@ -4,6 +4,9 @@
 
 assert(is_mac || is_ios)
 
+# Note: This source_set is depended on only by //media. In the component build,
+# if other component targets also depend on it, multiple copies of the ObjC
+# classes declared in the files below will cause warnings at run-time.

[Dirk Pranke, 2016/05/06 22:10:07]

You can/should use the `visibility` variable to enforce this, then.

[Robert Sesek, 2016/05/06 22:20:49]

Done.

 source_set("mac") {
   set_sources_assignment_filter([])
   sources = [
@@ -24,13 +27,14 @@ source_set("mac") {
     ]
     libs = [
       "AVFoundation.framework",
-
-      # Required by video_frame_mac.cc.
-      "CoreVideo.framework",
+      "CoreVideo.framework",  # Required by video_frame_mac.cc.
     ]
   }
   set_sources_assignment_filter(sources_assignment_filter)
-  configs += [ "//media:media_config" ]
+  configs += [
+    "//media:media_config",
+    "//media:media_implementation",
+  ]
 }
 
 source_set("unittests") {