Fix audio glitch when audio stream first starts up.

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"
@@ skipping 15 matching lines @@
 uint32 AudioSyncReader::Read(void* data, uint32 size) {
   uint32 max_size = media::PacketSizeSizeInBytes(
       shared_memory_->created_size());
   uint32 read_size = std::min(media::GetActualDataSizeInBytes(shared_memory_,
                                                               max_size),
                               size);
 
   // Get the data from the buffer.
   memcpy(data, shared_memory_->memory(), read_size);
 
+  // If amount read was less than requested, then zero out the remainder.
+  if (read_size < size)
+    memset(static_cast<char*>(data) + read_size, 0, size - read_size);
+
   // Zero out the entire buffer.
   memset(shared_memory_->memory(), 0, max_size);
 
   // Store max length of data into buffer, in case client does not do that.
   media::SetActualDataSizeInBytes(shared_memory_, max_size, max_size);
 
   return read_size;
 }
 
 void AudioSyncReader::Close() {
@@ skipping 25 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