Add an initial revision of an audio server.

services/media/audio/platform/generic/mixers/no_op.cc

+// Copyright 2015 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 "base/logging.h"
+#include "services/media/audio/platform/generic/mixers/no_op.h"
+
+namespace mojo {
+namespace media {
+namespace audio {
+namespace mixers {
+
+bool NoOp::Mix(void*       dst,
+               uint32_t    dst_frames,
+               uint32_t*   dst_offset,
+               const void* src,
+               uint32_t    frac_src_frames,
+               uint32_t*   frac_src_offset,
+               uint32_t    frac_step_size,
+               bool        accumulate) {
+  DCHECK_LT(*dst_offset, dst_frames);
+  DCHECK_LT(*frac_src_offset, frac_src_frames);
+
+  uint32_t frames_produced = ((frac_src_frames - *frac_src_offset)
+                           + frac_step_size - 1) / frac_step_size;
+
+  if (frames_produced > (dst_frames - *dst_offset)) {
+      frames_produced = (dst_frames - *dst_offset);
+  }
+
+  *dst_offset      += frames_produced;
+  *frac_src_offset += frames_produced * frac_step_size;
+
+  return (*frac_src_offset >= frac_src_frames);
+}
+
+}  // namespace mixers
+}  // namespace audio
+}  // namespace media
+}  // namespace mojo