Don't background processes with active audio output.

content/browser/renderer_host/render_process_host_impl.cc

Index: content/browser/renderer_host/render_process_host_impl.cc
diff --git a/content/browser/renderer_host/render_process_host_impl.cc b/content/browser/renderer_host/render_process_host_impl.cc
index 6f45e67a50e8481e5fb2a3df79722d87ca6108d7..3a070cb87aa801d9501358c2e6d0de2904aca254 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -1938,6 +1938,10 @@ void RenderProcessHostImpl::SetBackgrounded(bool backgrounded) {
   if (!child_process_launcher_.get() || child_process_launcher_->IsStarting())
     return;
 
+  // Don't background processes which have active audio streams.
+  if (backgrounded_ && audio_renderer_host_->HasActiveAudio())
+    return;
+
 #if defined(OS_WIN)
   // The cbstext.dll loads as a global GetMessage hook in the browser process
   // and intercepts/unintercepts the kernel32 API SetPriorityClass in a