Change 'mute' parameter of MediaChannel::SetAudioSend()/SetVideoSend() to 'enable'.

BUG=webrtc:4690

Review URL: https://codereview.webrtc.org/1378513003

Cr-Commit-Position: refs/heads/master@{#10130}
diff --git a/talk/media/base/mediachannel.h b/talk/media/base/mediachannel.h
index 9c9e8c4..9ed662d 100644
--- a/talk/media/base/mediachannel.h
+++ b/talk/media/base/mediachannel.h
@@ -1070,7 +1070,8 @@
   // Starts or stops sending (and potentially capture) of local audio.
   virtual bool SetSend(SendFlags flag) = 0;
   // Configure stream for sending.
-  virtual bool SetAudioSend(uint32 ssrc, bool mute, const AudioOptions* options,
+  virtual bool SetAudioSend(uint32 ssrc, bool enable,
+                            const AudioOptions* options,
                             AudioRenderer* renderer) = 0;
   // Sets the renderer object to be used for the specified remote audio stream.
   virtual bool SetRemoteRenderer(uint32 ssrc, AudioRenderer* renderer) = 0;
@@ -1143,7 +1144,7 @@
   // Starts or stops transmission (and potentially capture) of local video.
   virtual bool SetSend(bool send) = 0;
   // Configure stream for sending.
-  virtual bool SetVideoSend(uint32 ssrc, bool mute,
+  virtual bool SetVideoSend(uint32 ssrc, bool enable,
                             const VideoOptions* options) = 0;
   // Sets the renderer object to be used for the specified stream.
   // If SSRC is 0, the renderer is used for the 'default' stream.