Added #ifdef to allow Chromium to enable proprietary codecs.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 05adc1a5e627f9259797292953ca33a3b7799472..6aad19325c20f5db52f73e155b51b654733d7b79 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -189,6 +189,10 @@
     # Whether usage of OpenMAX is enabled.
     'enable_openmax%': 0,
 
+    # Whether proprietary audio/video codecs are assumed to be included with
+    # this build (only meaningful if branding!=Chrome).
+    'proprietary_codecs%': 0,
+
     # TODO(bradnelson): eliminate this when possible.
     # To allow local gyp files to prevent release.vsprops from being included.
     # Yes(1) means include release.vsprops.
@@ -400,6 +404,9 @@
       ['chromeos==1', {
         'defines': ['OS_CHROMEOS=1'],
       }],
+      ['proprietary_codecs==1', {
+        'defines': ['USE_PROPRIETARY_CODECS'],
+      }],
       ['fastbuild!=0', {
         'conditions': [
           # Finally, for Windows, we simply turn on profiling.