Forward the number of skipped frames by the OS in audio playout.

media/audio/audio_output_controller.h

Index: media/audio/audio_output_controller.h
diff --git a/media/audio/audio_output_controller.h b/media/audio/audio_output_controller.h
index 7820665440b4e0316e8d66a8fcfcdaade1d302db..1e831e2138cc98d100a66b2a5079028c9938be94 100644
--- a/media/audio/audio_output_controller.h
+++ b/media/audio/audio_output_controller.h
@@ -8,6 +8,7 @@
 #include "base/atomic_ref_count.h"
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
+#include "base/threading/thread_checker.h"
 #include "base/timer/timer.h"
 #include "build/build_config.h"
 #include "media/audio/audio_io.h"
@@ -82,8 +83,12 @@ class MEDIA_EXPORT AudioOutputController
 
     // Notify the synchronous reader the number of bytes in the
     // AudioOutputController not yet played. This is used by SyncReader to
-    // prepare more data and perform synchronization.
-    virtual void UpdatePendingBytes(uint32 bytes) = 0;
+    // prepare more data and perform synchronization. Also inform about if any
+    // frames has been skipped by the consumer. The source can handle this

[tommi (sloooow) - chröme, 2015/12/08 08:34:51]

Maybe I'm misunderstanding the context but it seems like 'producer' might be
more fitting than 'consumer' since the SyncReader is a consumer and whatever
higher up it feeds the data too.
'source' also feels backwards to me since it's the source that's providing this
data and it's up to the recipient of the data, i.e. the actual consumer, to
handle it.

[Henrik Grunell, 2015/12/08 09:30:34]

OK. Well, it refers to the actual audio data, which flows towards the OS, who is
the end consumer for that data. This function and its parameters go in the
opposite direction as a requester for the data. I see that the comment can be
confusing. We should agree on the terminology, or I can clarify this in the
text.

[tommi (sloooow) - chröme, 2015/12/08 10:08:09]

ah, I was confused about which direction we were going.  what about using
'renderer'?

[Henrik Grunell, 2015/12/08 11:12:32]

Sounds good, but I also added "(typically the OS)" to not be confused with
render process...

+    // appropriately depending on the type of source. An ordinary file playout
+    // would ignore this.
+    virtual void UpdatePendingBytes(uint32_t bytes,
+                                    uint32_t frames_skipped) = 0;
 
     // Attempts to completely fill |dest|, zeroing |dest| if the request can not
     // be fulfilled (due to timeout).
@@ -153,7 +158,9 @@ class MEDIA_EXPORT AudioOutputController
                           const base::Closure& callback);
 
   // AudioSourceCallback implementation.
-  int OnMoreData(AudioBus* dest, uint32 total_bytes_delay) override;
+  int OnMoreData(AudioBus* dest,
+                 uint32_t total_bytes_delay,
+                 uint32_t frames_skipped) override;
   void OnError(AudioOutputStream* stream) override;
 
   // AudioDeviceListener implementation.  When called AudioOutputController will