[Mac] Maximise timer slack for background tabs

content/common/child_process_messages.h

 // 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.
 
 // Common IPC messages used for child processes.
 // Multiply-included message file, hence no include guard.
 
 #include <string>
 #include <vector>
 
@@ skipping 93 matching lines @@
 IPC_MESSAGE_CONTROL1(ChildProcessMsg_GetChildProfilerData,
                      int /* sequence_number */)
 
 // Send to all the child processes to send back histogram data.
 IPC_MESSAGE_CONTROL1(ChildProcessMsg_GetChildHistogramData,
                      int /* sequence_number */)
 
 // Sent to child processes to dump their handle table.
 IPC_MESSAGE_CONTROL0(ChildProcessMsg_DumpHandles)
 
-#if defined(OS_WIN)
 // Sent to child processes to tell them to enter or leave background mode.
 IPC_MESSAGE_CONTROL1(ChildProcessMsg_SetProcessBackgrounded,
                      bool /* background */)
-#endif
 
 #if defined(USE_TCMALLOC)
 // Sent to child process to request tcmalloc stats.
 IPC_MESSAGE_CONTROL0(ChildProcessMsg_GetTcmallocStats)
 #endif
 
 ////////////////////////////////////////////////////////////////////////////////
 // Messages sent from the child process to the browser.
 
 IPC_MESSAGE_CONTROL0(ChildProcessHostMsg_ShutdownRequest)
@@ skipping 57 matching lines @@
                      std::string /* output */)
 #endif
 
 // Asks the browser to create a gpu memory buffer.
 IPC_SYNC_MESSAGE_CONTROL4_1(ChildProcessHostMsg_SyncAllocateGpuMemoryBuffer,
                             uint32 /* width */,
                             uint32 /* height */,
                             uint32 /* internalformat */,
                             uint32 /* usage */,
                             gfx::GpuMemoryBufferHandle)