Replace media::Limits struct with media::limits namespace and update documentation.

media/audio/audio_parameters.cc

Index: media/audio/audio_parameters.cc
diff --git a/media/audio/audio_parameters.cc b/media/audio/audio_parameters.cc
index 45c98d9d5a2ce8315f76fcf1989ca2c1444aae2c..4395481764a626a3f6837742e0dac40be9aad487 100644
--- a/media/audio/audio_parameters.cc
+++ b/media/audio/audio_parameters.cc
@@ -28,12 +28,12 @@ AudioParameters::AudioParameters(Format format, ChannelLayout channel_layout,
 
 bool AudioParameters::IsValid() const {
   return (format >= 0) && (format < AUDIO_LAST_FORMAT) &&
-      (channels > 0) && (channels <= media::Limits::kMaxChannels) &&
-      (sample_rate > 0) && (sample_rate <= media::Limits::kMaxSampleRate) &&
+      (channels > 0) && (channels <= media::limits::kMaxChannels) &&
+      (sample_rate > 0) && (sample_rate <= media::limits::kMaxSampleRate) &&
       (bits_per_sample > 0) &&
-      (bits_per_sample <= media::Limits::kMaxBitsPerSample) &&
+      (bits_per_sample <= media::limits::kMaxBitsPerSample) &&
       (samples_per_packet > 0) &&
-      (samples_per_packet <= media::Limits::kMaxSamplesPerPacket);
+      (samples_per_packet <= media::limits::kMaxSamplesPerPacket);
 }
 
 int AudioParameters::GetPacketSize() const {