Convert USE_PROPRIETARY_CODECS to a buildflag header.

media/BUILD.gn

Index: media/BUILD.gn
diff --git a/media/BUILD.gn b/media/BUILD.gn
index 279eab9bd6e88635fb965707e1c7d4a31057f503..6804b04e63e618b1b989236e8b167275aa7b566d 100644
--- a/media/BUILD.gn
+++ b/media/BUILD.gn
@@ -25,6 +25,7 @@ buildflag_header("media_features") {
     "ENABLE_MSE_MPEG2TS_STREAM_PARSER=$enable_mse_mpeg2ts_stream_parser",
     "ENABLE_MEDIA_REMOTING=$enable_media_remoting",
     "ENABLE_WEBRTC=$enable_webrtc",
+    "USE_PROPRIETARY_CODECS=$proprietary_codecs",
   ]
 }
 
@@ -274,11 +275,30 @@ component("media") {
   defines = []
   deps = [
     ":cdm_api",
+    "//base",
+    "//base:i18n",
+    "//base/third_party/dynamic_annotations",
+    "//crypto",
+    "//crypto:platform",
+    "//gpu/command_buffer/client:gles2_interface",
+    "//gpu/command_buffer/common",
+    "//skia",
+    "//third_party/libwebm",
+    "//third_party/libyuv",
+    "//ui/events:events_base",
+    "//ui/gfx",
+    "//ui/gfx/geometry",
+    "//ui/gl:gl",
+    "//url",
   ]
 
   public_configs = [ "//third_party/libwebm:libwebm_config" ]
   public_deps = [
     ":filters_common",
+    ":media_features",
+    ":shared_memory_support",
+    "//media/audio",
+    "//media/base",
   ]
 
   include_dirs = [ "." ]
@@ -496,31 +516,6 @@ component("media") {
       "device_monitors/device_monitor_udev.h",
     ]
   }
-
-  public_deps += [
-    ":media_features",
-    ":shared_memory_support",
-    "//media/audio",
-    "//media/base",
-  ]
-
-  deps += [
-    "//base",
-    "//base:i18n",
-    "//base/third_party/dynamic_annotations",
-    "//crypto",
-    "//crypto:platform",
-    "//gpu/command_buffer/client:gles2_interface",
-    "//gpu/command_buffer/common",
-    "//skia",
-    "//third_party/libwebm",
-    "//third_party/libyuv",
-    "//ui/events:events_base",
-    "//ui/gfx",
-    "//ui/gfx/geometry",
-    "//ui/gl:gl",
-    "//url",
-  ]
 }
 
 static_library("cdm_paths") {