Clean up histogram'd media enum max values.

media/base/video_decoder_config.h

Index: media/base/video_decoder_config.h
diff --git a/media/base/video_decoder_config.h b/media/base/video_decoder_config.h
index 3f7db4e6ca8b5a61ec7aec83101748e9fec0af29..4dcf5154dee4441b8154833726701394b93ded34 100644
--- a/media/base/video_decoder_config.h
+++ b/media/base/video_decoder_config.h
@@ -19,7 +19,7 @@ namespace media {
 enum VideoCodec {
   // These values are histogrammed over time; do not change their ordinal
   // values.  When deleting a codec replace it with a dummy value; when adding a
-  // codec, do so at the bottom (and update kVideoCodecMax).
+  // codec, do so at the bottom (but not below kVideoCodecHistogramMax!).
   kUnknownVideoCodec = 0,
   kCodecH264,
   kCodecVC1,
@@ -33,7 +33,8 @@ enum VideoCodec {
   // The only acceptable time to add a new codec is if there is production code
   // that uses said codec in the same CL.
 
-  kVideoCodecMax = kCodecVP9  // Must equal the last "real" codec above.
+  // Must always be the last value:
+  kVideoCodecHistogramMax,
 };
 
 // Video stream profile.  This *must* match PP_VideoDecoder_Profile.
@@ -62,7 +63,7 @@ enum VideoCodecProfile {
   VP9PROFILE_MIN = 12,
   VP9PROFILE_MAIN = VP9PROFILE_MIN,
   VP9PROFILE_MAX = VP9PROFILE_MAIN,
-  VIDEO_CODEC_PROFILE_MAX = VP9PROFILE_MAX,
+  VIDEO_CODEC_PROFILE_HISTOGRAM_MAX,  // Must always be the last value.
 };
 
 class MEDIA_EXPORT VideoDecoderConfig {