Privitize WaitTillDataReady() and DataReady().

content/browser/renderer_host/media/audio_sync_reader.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/browser/renderer_host/media/audio_sync_reader.h"
 
 #include <algorithm>
 
 #include "base/metrics/histogram.h"
 #include "base/process_util.h"
@@ skipping 50 matching lines @@
     // Store unknown length of data into buffer, so we later
     // can find out if data became available.
     media::SetUnknownDataSize(shared_memory_, packet_size_);
   }
 
   if (socket_) {
     socket_->Send(&bytes, sizeof(bytes));
   }
 }
 
-int AudioSyncReader::Read(AudioBus* source, AudioBus* dest) {
+int AudioSyncReader::Read(bool block, const AudioBus* source, AudioBus* dest) {
   ++renderer_callback_count_;
-  if (!DataReady())
+  if (!DataReady()) {
     ++renderer_missed_callback_count_;
 
+    if (block)
+      WaitTillDataReady();
+  }
+
   // Copy optional synchronized live audio input for consumption by renderer
   // process.
   if (source && input_bus_) {
     DCHECK_EQ(source->channels(), input_bus_->channels());
     // TODO(crogers): In some cases with device and sample-rate changes
     // it's possible for an AOR to insert a resampler in the path.
     // Because this is used with the Web Audio API, it'd be better
     // to bypass the device change handling in AOR and instead let
     // the renderer-side Web Audio code deal with this.
     if (source->frames() == input_bus_->frames() &&
@@ skipping 69 matching lines @@
     base::ProcessHandle process_handle,
     base::FileDescriptor* foreign_handle) {
   foreign_handle->fd = foreign_socket_->handle();
   foreign_handle->auto_close = false;
   if (foreign_handle->fd != -1)
     return true;
   return false;
 }
 #endif
 
+void AudioSyncReader::WaitTillDataReady() {
+  base::TimeTicks start = base::TimeTicks::Now();
+  const base::TimeDelta kMaxWait = base::TimeDelta::FromMilliseconds(20);

[henrika (OOO until Aug 14), 2013/06/03 07:57:18]

Is it OK to use hard coded values here or should we break out kWait-consts with
a comment for each?

[DaleCurtis, 2013/06/04 00:35:41]

I think it's okay as is. davemoore@ just cleaned this up in a previous CL. I'm
only moving things around.

+#if defined(OS_WIN)
+  // Sleep(0) on windows lets the other threads run.

[henrika (OOO until Aug 14), 2013/06/03 07:57:18]

nit, Windows

[DaleCurtis, 2013/06/04 00:35:41]

Done.

+  const base::TimeDelta kSleep = base::TimeDelta::FromMilliseconds(0);
+#else
+  // We want to sleep for a bit here, as otherwise a backgrounded renderer won't
+  // get enough cpu to send the data and the high priority thread in the browser
+  // will use up a core causing even more skips.
+  const base::TimeDelta kSleep = base::TimeDelta::FromMilliseconds(2);
+#endif
+  base::TimeDelta time_since_start;
+  do {
+    base::PlatformThread::Sleep(kSleep);
+    time_since_start = base::TimeTicks::Now() - start;
+  } while (!DataReady() && time_since_start < kMaxWait);
+  UMA_HISTOGRAM_CUSTOM_TIMES("Media.AudioOutputControllerDataNotReady",
+                             time_since_start,
+                             base::TimeDelta::FromMilliseconds(1),
+                             base::TimeDelta::FromMilliseconds(1000),
+                             50);
+}
+
 }  // namespace content