Don't background processes with active audio output.

content/browser/renderer_host/render_process_host_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Represents the browser side of the browser <--> renderer communication
 // channel. There will be one RenderProcessHost per renderer process.
 
 #include "content/browser/renderer_host/render_process_host_impl.h"
 
 #include <algorithm>
@@ skipping 1920 matching lines @@
 }
 
 void RenderProcessHostImpl::SetBackgrounded(bool backgrounded) {
   // Note: we always set the backgrounded_ value.  If the process is NULL
   // (and hence hasn't been created yet), we will set the process priority
   // later when we create the process.
   backgrounded_ = 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
   // background thread. If the UI thread invokes this API just when it is
   // intercepted the stack is messed up on return from the interceptor
   // which causes random crashes in the browser process. Our hack for now
   // is to not invoke the SetPriorityClass API if the dll is loaded.
   if (GetModuleHandle(L"cbstext.dll"))
     return;
 #endif  // OS_WIN
@@ skipping 122 matching lines @@
     mojo::ScopedMessagePipeHandle handle) {
   mojo_activation_required_ = true;
   MaybeActivateMojo();
 
   mojo::AllocationScope scope;
   mojo_application_host_->service_provider()->ConnectToService(service_name,
                                                                handle.Pass());
 }
 
 }  // namespace content