Collapse AudioRendererMixer and OnMoreDataResampler into AudioTransform.

media/base/fake_audio_render_callback.h

Index: media/base/fake_audio_render_callback.h
diff --git a/media/base/fake_audio_render_callback.h b/media/base/fake_audio_render_callback.h
index 760e39d6e9039c3fd40bf3aef74d206f6c8f9d1c..97afa54a5485f8ba21531fc586b5e16bbf5a51ac 100644
--- a/media/base/fake_audio_render_callback.h
+++ b/media/base/fake_audio_render_callback.h
@@ -6,13 +6,17 @@
 #define MEDIA_BASE_FAKE_AUDIO_RENDER_CALLBACK_H_
 
 #include "media/base/audio_renderer_sink.h"
+#include "media/base/audio_transform.h"
 #include "testing/gmock/include/gmock/gmock.h"
 
 namespace media {
 
 // Fake RenderCallback which will fill each request with a sine wave.  Sine
 // state is kept across callbacks.  State can be reset to default via reset().
-class FakeAudioRenderCallback : public AudioRendererSink::RenderCallback {
+// Also provide an interface to AudioTransformInput.
+class FakeAudioRenderCallback
+    : public AudioRendererSink::RenderCallback,
+      public AudioTransform::AudioTransformInput {

[miu, 2012/11/12 20:51:59]

I wonder whether it makes sense for AudioRendererSink::RenderCallback inherit
the AudioTransform::AudioTransformInput interface, and provide it's own default
implementation of ProvideAudioTransformInput() (which just calls Render())?

Is there a use case where a implementer of AudioRendererSink::RenderCallback
would do something different for ProvideAudioTransformInput()?

[DaleCurtis, 2012/11/12 21:23:53]

I considered that, but at present it doesn't seem worth the yak shave since most
callers will never interact with an AudioTransform directly.

On differences: one returns a float volume() while the other returns the number
of frames written to the bus. They also use an integer delay mechanism vs
TimeDelta.

Long term I could see us migrating to having the interfaces nearly the same, but
not presently.

  public:
   // The function used to fulfill Render() is f(x) = sin(2 * PI * x * |step|),
   // where x = [|number_of_frames| * m, |number_of_frames| * (m + 1)] and m =
@@ -22,9 +26,14 @@ class FakeAudioRenderCallback : public AudioRendererSink::RenderCallback {
 
   // Renders a sine wave into the provided audio data buffer.  If |half_fill_|
   // is set, will only fill half the buffer.
-  int Render(AudioBus* audio_bus, int audio_delay_milliseconds) OVERRIDE;
+  virtual int Render(AudioBus* audio_bus,
+                     int audio_delay_milliseconds) OVERRIDE;
   MOCK_METHOD0(OnRenderError, void());
 
+  // AudioTransform::ProvideAudioTransformInput implementation.
+  virtual float ProvideAudioTransformInput(
+      AudioBus* audio_bus, base::TimeDelta buffer_delay) OVERRIDE;
+
   // Toggles only filling half the requested amount during Render().
   void set_half_fill(bool half_fill) { half_fill_ = half_fill; }
 
@@ -35,11 +44,15 @@ class FakeAudioRenderCallback : public AudioRendererSink::RenderCallback {
   // no Render() call occurred.
   int last_audio_delay_milliseconds() { return last_audio_delay_milliseconds_; }
 
+  // Set volume information used by ProvideAudioTransformInput().
+  void set_volume(float volume) { volume_ = volume; }
+
  private:
   bool half_fill_;
   double x_;
   double step_;
   int last_audio_delay_milliseconds_;
+  float volume_;
 
   DISALLOW_COPY_AND_ASSIGN(FakeAudioRenderCallback);
 };