Fix problem when we did not play beginning of HTML5 audio stream in low latency mode.

content/browser/renderer_host/media/audio_sync_reader.cc

 // Copyright (c) 2011 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/process_util.h"
 #include "base/shared_memory.h"
 #include "base/threading/platform_thread.h"
 #include "media/audio/audio_buffers_state.h"
 #include "media/audio/audio_util.h"
 
 const int kMinIntervalBetweenReadCallsInMs = 10;
 
 AudioSyncReader::AudioSyncReader(base::SharedMemory* shared_memory)
     : shared_memory_(shared_memory) {
 }
 
 AudioSyncReader::~AudioSyncReader() {
 }
 
+bool AudioSyncReader::DataReady() {
+  return !media::IsUnknownDataSize(
+      shared_memory_,
+      media::PacketSizeSizeInBytes(shared_memory_->created_size()));
+}
+
 // media::AudioOutputController::SyncReader implementations.
 void AudioSyncReader::UpdatePendingBytes(uint32 bytes) {
+  if (bytes != static_cast<uint32>(media::AudioOutputController::kPauseMark)) {
+    // Store unknown length of data into buffer, so we later
+    // can find out if data became available.
+    media::SetUnknownDataSize(
+        shared_memory_,
+        media::PacketSizeSizeInBytes(shared_memory_->created_size()));
+  }
   socket_->Send(&bytes, sizeof(bytes));
 }
 
 uint32 AudioSyncReader::Read(void* data, uint32 size) {
   uint32 max_size = media::PacketSizeSizeInBytes(
       shared_memory_->created_size());
 
 #if defined(OS_WIN)
   // HACK: yield if reader is called too often.
   // Problem is lack of synchronization between host and renderer. We cannot be
   // sure if renderer already filled the buffer, and due to all the plugins we
   // cannot change the API, so we yield if previous call was too recent.
   // Optimization: if renderer is "new" one that writes length of data we can
   // stop yielding the moment length is written -- not ideal solution,
   // but better than nothing.
-  while (media::IsUnknownDataSize(shared_memory_, max_size) &&
+  while (!DataReady() &&
          ((base::Time::Now() - previous_call_time_).InMilliseconds() <
           kMinIntervalBetweenReadCallsInMs)) {
     base::PlatformThread::YieldCurrentThread();
   }
   previous_call_time_ = base::Time::Now();
 #endif
 
   uint32 read_size = std::min(media::GetActualDataSizeInBytes(shared_memory_,
                                                               max_size),
                               size);
@@ skipping 44 matching lines @@
 bool AudioSyncReader::PrepareForeignSocketHandle(
     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