Replace WIDEVINE_CDM_AVAILABLE with a gyp define 'enable_widevine_cdm'.

media/media_options.gni

Index: media/media_options.gni
diff --git a/media/media_options.gni b/media/media_options.gni
index c2b470930784a99c50d4efe48b7f642365d3c39f..de802ae65330a4f7a09ac91f7ba4aeecf55074f6 100644
--- a/media/media_options.gni
+++ b/media/media_options.gni
@@ -49,6 +49,13 @@ declare_args() {
   # the typical PPAPI based CDM is not available.
   enable_browser_cdms = is_android
 
+  # Widevine CDM is enabled by default for Chrome builds, and is a platform
+  # feature on Android.
+  enable_widevine = is_chrome_branded || is_android
+
+  # Widevine is distributed as a component for Mac and Win.
+  widevine_cdm_is_component = is_mac || is_win

[ddorwin, 2014/12/02 23:31:56]

ditto

+
   # TODO(GYP): This should be a platform define.
   is_openbsd = false
 }