Add support for passing an arbitrary parameter to an IPC message handler. The motivation is for Web…

content/common/view_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.
 
 // IPC messages for page rendering.
 // Multiply-included message file, hence no include guard.
 
 #include "base/memory/shared_memory.h"
 #include "base/process/process.h"
 #include "base/strings/string16.h"
@@ skipping 1253 matching lines @@
 IPC_MESSAGE_CONTROL1(ViewHostMsg_ForwardToWorker,
                      IPC::Message /* message */)
 
 // Tells the browser that a specific Appcache manifest in the current page
 // was accessed.
 IPC_MESSAGE_ROUTED2(ViewHostMsg_AppCacheAccessed,
                     GURL /* manifest url */,
                     bool /* blocked by policy */)
 
 // Initiates a download based on user actions like 'ALT+click'.
-IPC_MESSAGE_ROUTED4(ViewHostMsg_DownloadUrl,
-                    GURL     /* url */,
-                    content::Referrer /* referrer */,
-                    base::string16 /* suggested_name */,
-                    bool /* use prompt for save location */)
+IPC_MESSAGE_CONTROL5(ViewHostMsg_DownloadUrl,
+                     int /* render_view_id */,
+                     GURL /* url */,
+                     content::Referrer /* referrer */,
+                     base::string16 /* suggested_name */,
+                     bool /* use prompt for save location */)
 
 // Used to go to the session history entry at the given offset (ie, -1 will
 // return the "back" item).
 IPC_MESSAGE_ROUTED1(ViewHostMsg_GoToEntryAtOffset,
                     int /* offset (from current) of history item to get */)
 
 // Sent from an inactive renderer for the browser to route to the active
 // renderer, instructing it to close.
 IPC_MESSAGE_ROUTED0(ViewHostMsg_RouteCloseEvent)
 
@@ skipping 473 matching lines @@
 // synchronously (see crbug.com/120597). This IPC message sends the character
 // bounds after every composition change to always have correct bound info.
 IPC_MESSAGE_ROUTED2(ViewHostMsg_ImeCompositionRangeChanged,
                     gfx::Range /* composition range */,
                     std::vector<gfx::Rect> /* character bounds */)
 #endif
 
 // Adding a new message? Stick to the sort order above: first platform
 // independent ViewMsg, then ifdefs for platform specific ViewMsg, then platform
 // independent ViewHostMsg, then ifdefs for platform specific ViewHostMsg.