Control process backgrounding from within the child process on Windows.

content/child/child_thread.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.
 
 #include "content/child/child_thread.h"
 
 #include <signal.h>
 
 #include <string>
 
@@ skipping 422 matching lines @@
     IPC_MESSAGE_HANDLER(ChildProcessMsg_Shutdown, OnShutdown)
 #if defined(IPC_MESSAGE_LOG_ENABLED)
     IPC_MESSAGE_HANDLER(ChildProcessMsg_SetIPCLoggingEnabled,
                         OnSetIPCLoggingEnabled)
 #endif
     IPC_MESSAGE_HANDLER(ChildProcessMsg_SetProfilerStatus,
                         OnSetProfilerStatus)
     IPC_MESSAGE_HANDLER(ChildProcessMsg_GetChildProfilerData,
                         OnGetChildProfilerData)
     IPC_MESSAGE_HANDLER(ChildProcessMsg_DumpHandles, OnDumpHandles)
+#if defined(OS_WIN)
+    IPC_MESSAGE_HANDLER(ChildProcessMsg_SetProcessBackgrounded,
+                        OnProcessBackgrounded)
+#endif
 #if defined(USE_TCMALLOC)
     IPC_MESSAGE_HANDLER(ChildProcessMsg_GetTcmallocStats, OnGetTcmallocStats)
 #endif
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
 
   if (handled)
     return true;
 
   if (msg.routing_id() == MSG_ROUTING_CONTROL)
@@ skipping 88 matching lines @@
   // race conditions if the process refcount is 0 but there's an IPC message
   // inflight that would addref it.
   Send(new ChildProcessHostMsg_ShutdownRequest);
 }
 
 void ChildThread::EnsureConnected() {
   VLOG(0) << "ChildThread::EnsureConnected()";
   base::KillProcess(base::GetCurrentProcessHandle(), 0, false);
 }
 
+#if defined(OS_WIN)
+void ChildThread::OnProcessBackgrounded(bool background) {
+  base::Process::Current().SetProcessBackgrounded(background);

[nasko, 2014/05/28 23:08:37]

Out of curiosity, does that work from inside the sandbox?

[DaleCurtis, 2014/05/29 00:06:59]

Yup, I've confirmed the cpu, io priorities of the processes backgrounded have
gone from "6 (below normal), normal"  to "4 (idle), very low"

+}
+#endif
+
 }  // namespace content