Support removing b=AS bandwidth constraints.

webrtc/media/engine/webrtcmediaengine.cc

 /*
  *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 189 matching lines @@
   } else {
     config.min_bitrate_bps = 0;
   }
   if (codec.GetParam(kCodecParamStartBitrate, &bitrate_kbps) &&
       bitrate_kbps > 0) {
     config.start_bitrate_bps = bitrate_kbps * 1000;
   } else {
     // Do not reconfigure start bitrate unless it's specified and positive.
     config.start_bitrate_bps = -1;
   }
-  if (codec.GetParam(kCodecParamMaxBitrate, &bitrate_kbps) &&
-      bitrate_kbps > 0) {
-    config.max_bitrate_bps = bitrate_kbps * 1000;
-  } else {
-    config.max_bitrate_bps = -1;
-  }
+  // Codec max bitrate should be set and capped by encoder config, not global
+  // bitrate config.

[Taylor Brandstetter, 2017/03/09 23:48:38]

nit: This seems independent enough to warrant being in a standalone CL.

Also, this comment is a little confusing to me. Maybe something like this would
be more clear:

"The global max bitrate should only be restricted by 'b=AS', and not by
codec-specific bitrate limits, so leave it as -1 here. The codec-specific
bitrate limits will be enforced using the encoder configuration rather than the
global BitrateConfig."

[stefan-webrtc, 2017/03/10 08:14:53]

I agree that we should do this independently. And I'm pretty sure there are
applications relying on this, which is why it hasn't been fixed yet...

Let's talk offline about what needs to be done to fix this.

[pbos-webrtc, 2017/03/10 18:52:09]

Abandoned.

+  config.max_bitrate_bps = -1;
   return config;
 }
 }  // namespace cricket