Cast: Enable high-resolution timers while casting.

chrome/renderer/media/cast_session_delegate.cc

 // Copyright 2013 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 "chrome/renderer/media/cast_session_delegate.h"
 
 #include "base/callback_helpers.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/single_thread_task_runner.h"
@@ skipping 19 matching lines @@
 using media::cast::VideoSenderConfig;
 
 static base::LazyInstance<CastThreads> g_cast_threads =
     LAZY_INSTANCE_INITIALIZER;
 
 CastSessionDelegateBase::CastSessionDelegateBase()
     : io_task_runner_(
           content::RenderThread::Get()->GetIOMessageLoopProxy()),
       weak_factory_(this) {
   DCHECK(io_task_runner_.get());
+#if defined(OS_WIN)
+  if (!base::Time::ActivateHighResolutionTimer(true)) {

[miu, 2015/05/07 20:04:34]

nit: This led me to think this only provides better time precision on the "old
machines."  But, as we discussed, it also affects the threading timeslices.  Can
you add a quick comment to that effect here?

+    LOG(WARNING) << "Failed to activate high resolution timers for cast.";
+  }
+#endif
 }
 
 CastSessionDelegateBase::~CastSessionDelegateBase() {
   DCHECK(io_task_runner_->BelongsToCurrentThread());
+#if defined(OS_WIN)
+  base::Time::ActivateHighResolutionTimer(false);
+#endif
 }
 
 void CastSessionDelegateBase::StartUDP(
     const net::IPEndPoint& local_endpoint,
     const net::IPEndPoint& remote_endpoint,
     scoped_ptr<base::DictionaryValue> options,
     const ErrorCallback& error_callback) {
   DCHECK(io_task_runner_->BelongsToCurrentThread());
 
   // CastSender uses the renderer's IO thread as the main thread. This reduces
@@ skipping 284 matching lines @@
     } else {
       cast_environment_->Logging()->InsertFrameEvent(
           it->timestamp,
           it->type,
           it->media_type,
           it->rtp_timestamp,
           it->frame_id);
     }
   }
 }