Add functionality to the renderer thread to purge memory. Not yet called....

chrome/common/render_messages_internal.h

 // Copyright (c) 2009 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.
 
 // This header is meant to be included in multiple passes, hence no traditional
 // header guard.
 // See ipc_message_macros.h for explanation of the macros and passes.
 
 #include <map>
 #include <string>
@@ skipping 121 matching lines @@
 
   // Tells the render view to switch the CSS to print media type, renders every
   // requested pages and switch back the CSS to display media type.
   IPC_MESSAGE_ROUTED0(ViewMsg_PrintPages)
 
   // Tells the render view that printing is done so it can clean up.
   IPC_MESSAGE_ROUTED2(ViewMsg_PrintingDone,
                       int /* document_cookie */,
                       bool /* success */)
 
+  // Tells the renderer to dump as much memory as it can, perhaps because we
+  // have memory pressure or the renderer is (or will be) paged out.  This
+  // should only result in purging objects we can recalculate, e.g. caches or
+  // JS garbage, not in purging irreplaceable objects.
+  IPC_MESSAGE_CONTROL0(ViewMsg_PurgeMemory)
+
   // Tells the render view that a ViewHostMsg_ScrollRect message was processed.
   // This signals the render view that it can send another ScrollRect message.
   IPC_MESSAGE_ROUTED0(ViewMsg_ScrollRect_ACK)
 
   // Message payload is a blob that should be cast to WebInputEvent
   IPC_MESSAGE_ROUTED0(ViewMsg_HandleInputEvent)
 
   // This message notifies the renderer that the next key event is bound to one
   // or more pre-defined edit commands. If the next key event is not handled
   // by webkit, the specified edit commands shall be executed against current
@@ skipping 1681 matching lines @@
   IPC_MESSAGE_CONTROL2(ViewHostMsg_DatabaseGetFileAttributes,
                        FilePath /* the name of the file */,
                        int32 /* a unique message ID */)
 
   // Asks the browser process to return the size of a DB file
   IPC_MESSAGE_CONTROL2(ViewHostMsg_DatabaseGetFileSize,
                        FilePath /* the name of the file */,
                        int32 /* a unique message ID */)
 
 IPC_END_MESSAGES(ViewHost)