Getting rid of AudioHardwareConfig and its synchronous IPC.

content/renderer/media/audio_renderer_sink_cache_impl.cc

Index: content/renderer/media/audio_renderer_sink_cache_impl.cc
diff --git a/content/renderer/media/audio_renderer_sink_cache_impl.cc b/content/renderer/media/audio_renderer_sink_cache_impl.cc
index 9fef7d0937b1dc594ee067d45f10a1ef6363b2ae..4401f7cf56a5fe17f1f636de5a165c8f517cbf18 100644
--- a/content/renderer/media/audio_renderer_sink_cache_impl.cc
+++ b/content/renderer/media/audio_renderer_sink_cache_impl.cc
@@ -79,16 +79,25 @@ media::OutputDeviceInfo AudioRendererSinkCacheImpl::GetSinkInfo(
     // Ignore session id.
     base::AutoLock auto_lock(cache_lock_);
 
-    auto cache_iter =
-        FindCacheEntry_Locked(source_render_frame_id, device_id,
-                              security_origin, false /* unused_only */);
-
-    if (cache_iter != cache_.end()) {
-      // A matching cached sink is found.
-      DVLOG(1) << "GetSinkInfo: address: " << cache_iter->sink.get()
-               << " - reused a cached sink.";
-
-      return cache_iter->sink->GetOutputDeviceInfo();
+    if (media::AudioDeviceDescription::IsDefaultDevice(device_id)) {
+      if (default_device_info_)
+        return default_device_info_.value();
+
+      // Otherwise, there is no default device cached.
+      DCHECK(FindCacheEntry_Locked(source_render_frame_id, device_id,
+                                   security_origin, false) == cache_.end());
+    } else {
+      // Looking up a cached non-default device.
+      auto cache_iter = FindCacheEntry_Locked(source_render_frame_id, device_id,
+                                              security_origin, false);
+
+      if (cache_iter != cache_.end()) {
+        // A matching cached sink is found.
+        DVLOG(1) << "GetSinkInfo: address: " << cache_iter->sink.get()
+                 << " - reused a cached sink.";
+
+        return cache_iter->sink->GetOutputDeviceInfo();
+      }
     }
 
     // No matching sink found, create a new one.
@@ -101,6 +110,10 @@ media::OutputDeviceInfo AudioRendererSinkCacheImpl::GetSinkInfo(
 
     // Cache a newly-created sink.
     cache_.push_back(cache_entry);
+
+    // Cache information for default output device.

[DaleCurtis, 2016/07/06 18:53:37]

Do we want to cache this? We'll carry over bugs around plugging in new default
devices when a renderer has been created and audio started. I.e., old parameters
will be used.

[o1ka, 2016/07/13 09:52:41]

removed

+    if (media::AudioDeviceDescription::IsDefaultDevice(device_id))
+      default_device_info_ = cache_entry.sink->GetOutputDeviceInfo();
   }
 
   // Schedule it for deletion.
@@ -122,7 +135,7 @@ scoped_refptr<media::AudioRendererSink> AudioRendererSinkCacheImpl::GetSink(
 
   auto cache_iter =
       FindCacheEntry_Locked(source_render_frame_id, device_id, security_origin,
-                            true /* unused_only */);
+                            true /* unused sink only */);
 
   if (cache_iter != cache_.end()) {
     // Found unused sink; mark it as used and return.
@@ -142,6 +155,10 @@ scoped_refptr<media::AudioRendererSink> AudioRendererSinkCacheImpl::GetSink(
 
   cache_.push_back(cache_entry);
 
+  // Update cached information for default output device.
+  if (media::AudioDeviceDescription::IsDefaultDevice(device_id))
+    default_device_info_ = cache_entry.sink->GetOutputDeviceInfo();
+
   DVLOG(1) << "GetSink: address: " << cache_entry.sink.get()
            << " - no unused cached sink found, created a new one."
            << " source_render_frame_id: " << source_render_frame_id