Make OS audio buffer size limits visible.

content/renderer/media/renderer_webaudiodevice_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/media/renderer_webaudiodevice_impl.h"
 
 #include <stddef.h>
 
 #include <string>
 
@@ skipping 47 matching lines @@
       break;
     case media::AudioLatency::LATENCY_RTC:
       return media::AudioLatency::GetRtcBufferSize(
           hardware_params.sample_rate(), hardware_params.frames_per_buffer());
       break;
     case media::AudioLatency::LATENCY_PLAYBACK:
       return media::AudioLatency::GetHighLatencyBufferSize(
           hardware_params.sample_rate(), 0);
       break;
     case media::AudioLatency::LATENCY_EXACT_MS:
-      // TODO(andrew.macpherson@soundtrap.com): http://crbug.com/708917
-      return std::min(4096,

[Raymond Toy, 2017/05/30 18:05:57]

Can't remember the actual value, but make this consistent with the playback
latency value.  The user should be able to specify a value up to the playback
latency.  Perhaps even using GetHighLatencyBufferSize to figure this out.

+      return std::min(media::AudioLatency::GetMaximumAudioBufferSize(
+                          hardware_params.sample_rate()),
                       media::AudioLatency::GetExactBufferSize(
                           base::TimeDelta::FromSecondsD(latency_hint.Seconds()),
                           hardware_params.sample_rate(),
-                          hardware_params.frames_per_buffer()));
+                          media::AudioLatency::GetMinimumAudioBufferSize(
+                              hardware_params.sample_rate())));
       break;
     default:
       NOTREACHED();
   }
   return 0;
 }
 
 int FrameIdFromCurrentContext() {
   // Assumption: This method is being invoked within a V8 call stack.  CHECKs
   // will fail in the call to frameForCurrentContext() otherwise.
@@ skipping 157 matching lines @@
 const scoped_refptr<base::SingleThreadTaskRunner>&
 RendererWebAudioDeviceImpl::GetMediaTaskRunner() {
   if (!media_task_runner_) {
     media_task_runner_ =
         RenderThreadImpl::current()->GetMediaThreadTaskRunner();
   }
   return media_task_runner_;
 }
 
 }  // namespace content