Experimental 'purging and suspending' backgrounded tabs behind the flag

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 <stdint.h>
 
 #include <string>
@@ skipping 100 matching lines @@
                      int /* shm_size */)
 
 // Send to all the child processes to send back histogram data.
 IPC_MESSAGE_CONTROL1(ChildProcessMsg_GetChildNonPersistentHistogramData,
                      int /* sequence_number */)
 
 // Sent to child processes to tell them to enter or leave background mode.
 IPC_MESSAGE_CONTROL1(ChildProcessMsg_SetProcessBackgrounded,
                      bool /* background */)
 
+// Sent to child processes to tell them to purge and suspend.
+IPC_MESSAGE_CONTROL0(ChildProcessMsg_PurgeAndSuspend)
+
 ////////////////////////////////////////////////////////////////////////////////
 // Messages sent from the child process to the browser.
 
 // A renderer sends this when it wants to create a connection to the GPU
 // process. The browser will create the GPU process if necessary, and will
 // return a handle to the channel via a GpuChannelEstablished message.
 IPC_SYNC_MESSAGE_CONTROL1_3(ChildProcessHostMsg_EstablishGpuChannel,
                             content::CauseForGpuLaunch,
                             int /* client id */,
                             IPC::ChannelHandle /* handle to channel */,
@@ skipping 75 matching lines @@
 IPC_SYNC_MESSAGE_CONTROL2_1(
     ChildProcessHostMsg_SyncAllocateLockedDiscardableSharedMemory,
     uint32_t /* size */,
     content::DiscardableSharedMemoryId,
     base::SharedMemoryHandle)
 
 // Informs the browser that the child deleted a block of discardable shared
 // memory.
 IPC_MESSAGE_CONTROL1(ChildProcessHostMsg_DeletedDiscardableSharedMemory,
                      content::DiscardableSharedMemoryId)