Audio related IPC messages and handlers from browser to renderer

Audio related IPC messages and handlers from browser to
renderer
1. Added 4 IPC messages and corresponding handlers for
audio:
  - RequestAudioPacket(int stream_id)
    Browser process is hungry for audio packet, notify
    renderer process to provide more.

  - NotifyAudioStreamCreated(int stream_id, SharedMemoryHandler
buffer, int len)
    Notify stream created event and provide buffer for
    filling in the future.

  - NotifyAudioStreamStateChanged(int stream_id, enum state, 
nt info)
    The internal state of the audio stream has chagned,
notify renderer
    process of the change. int info provides additional
information of the
    change, e.g. platform specific error code.

  - NotifyAudioStreamVolume(int stream_id, double left, double right)
    Notify the current volume for the audio stream.
2. Added methods to RenderView for creating audio streams
and delegate audio related requests to browser process with
IPC. Now the registration and bookkeeping of
AudioRendererImpl happens in RenderView (see
audio_renderers_). The reason being that the code is almost
just an base::IDMap that doesn't worth creating a new class.

[cpu_(ooo_6.6-7.5), 2009-02-18 20:37:01]

http://codereview.chromium.org/20410/diff/1011/31
File chrome/renderer/media/audio_renderer_impl.h (right):

http://codereview.chromium.org/20410/diff/1011/31#newcode9
Line 9: #include "chrome/common/render_messages.h"
I think we are not supposed to do that see:
http://groups.google.com/group/chromium-dev/browse_thread/thread/f349bf662c4a...

This might cause other re-structuring but it makes sense to me.

http://codereview.chromium.org/20410/diff/1011/32
File chrome/renderer/render_view.cc (right):

http://codereview.chromium.org/20410/diff/1011/32#newcode2875
Line 2875: DCHECK(renderer);
instead of the dcheck it seems better to me to do
if (!audio_renderer) {
  NOTREACHED();
  return;
}

http://codereview.chromium.org/20410/diff/1011/32#newcode2881
Line 2881: AudioRendererImpl* renderer = audio_renderers_.Lookup(stream_id);
renderer var name is confusing, change to audio_renderer or some other name with
audio in it.

[Alpha Left Google, 2009-02-18 21:50:31]

http://codereview.chromium.org/20410/diff/1011/31
File chrome/renderer/media/audio_renderer_impl.h (right):

http://codereview.chromium.org/20410/diff/1011/31#newcode9
Line 9: #include "chrome/common/render_messages.h"
On 2009/02/18 20:37:02, cpu wrote:
> I think we are not supposed to do that see:
>
http://groups.google.com/group/chromium-dev/browse_thread/thread/f349bf662c4a...
> 
> This might cause other re-structuring but it makes sense to me.
> 
> 

I've changed it to a forward declaration.

http://codereview.chromium.org/20410/diff/1011/32
File chrome/renderer/render_view.cc (right):

http://codereview.chromium.org/20410/diff/1011/32#newcode2875
Line 2875: DCHECK(renderer);
On 2009/02/18 20:37:02, cpu wrote:
> instead of the dcheck it seems better to me to do
> if (!audio_renderer) {
>   NOTREACHED();
>   return;
> }

Done.

[cpu_(ooo_6.6-7.5), 2009-02-18 23:35:06]

LGTM