Load CMA backend from shared library

chromecast/media/base/media_codec_support.h

Index: chromecast/media/base/media_codec_support.h
diff --git a/chromecast/media/base/media_codec_support.h b/chromecast/media/base/media_codec_support.h
index e961177ecb0c735308bc6af2cca3e960ec31ff36..c79ab5cfd6d919e97ce394687701ff7fea4c80a8 100644
--- a/chromecast/media/base/media_codec_support.h
+++ b/chromecast/media/base/media_codec_support.h
@@ -20,15 +20,11 @@ bool DefaultIsCodecSupported(const std::string&);
 namespace chromecast {
 namespace media {
 
-// This function should return a callback capable of deciding whether a given
-// codec (passed in as a string representation of the codec id conforming to
-// RFC 6381) is supported or not. The implementation of this function is
-// expected to be provided somewhere in the vendor platform-specific libraries
-// that will get linked with cast_shell_common target.
+// Returns the callback to decide whether a given codec (passed in as a string
+// representation of the codec id conforming to RFC 6381) is supported or not.
 net::IsCodecSupportedCB GetIsCodecSupportedOnChromecastCB();
 
 }  // namespace media
 }  // namespace chromecast
 
 #endif  // CHROMECAST_MEDIA_BASE_MEDIA_CODEC_SUPPORT_H_
-