media: Add out-of-line copy ctors for complex classes.

media/base/audio_decoder_config.h

Index: media/base/audio_decoder_config.h
diff --git a/media/base/audio_decoder_config.h b/media/base/audio_decoder_config.h
index a0e262f005d3343279ac3e5fa137549d4a203db8..c3489cc2a456ca8239a2430992feafa6ac61f568 100644
--- a/media/base/audio_decoder_config.h
+++ b/media/base/audio_decoder_config.h
@@ -68,6 +68,8 @@ class MEDIA_EXPORT AudioDecoderConfig {
                      const std::vector<uint8_t>& extra_data,
                      bool is_encrypted);
 
+  AudioDecoderConfig(const AudioDecoderConfig& other);
+
   ~AudioDecoderConfig();
 
   // Resets the internal state of this object. |codec_delay| is in frames.