use variadic macros/templates in IPC message implementation

content/renderer/input/input_event_filter.cc

 // Copyright 2013 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/renderer/input/input_event_filter.h"
 
 #include <utility>
 
 #include "base/auto_reset.h"
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/single_thread_task_runner.h"
 #include "base/thread_task_runner_handle.h"
 #include "base/trace_event/trace_event.h"
 #include "content/common/input/did_overscroll_params.h"
 #include "content/common/input/web_input_event_traits.h"
 #include "content/common/input_messages.h"
 #include "content/common/view_messages.h"
 #include "content/public/common/content_switches.h"
 #include "ipc/ipc_listener.h"
 #include "ipc/ipc_sender.h"
 #include "ui/events/blink/synchronous_input_handler_proxy.h"
 #include "ui/gfx/geometry/vector2d_f.h"
 
 using blink::WebInputEvent;
 
 #include "ipc/ipc_message_null_macros.h"
 #undef IPC_MESSAGE_DECL
-#define IPC_MESSAGE_DECL(kind, type, name, in, out, ilist, olist) \
-  case name::ID: return #name;
+#define IPC_MESSAGE_DECL(name, ...) \

[vmpstr, 2016/02/04 23:43:27]

Where is this used? I tried to see if you updated the callsites to use the first
parameter as name instead of third, but I can't really find where this is used
:)

[mdempsky, 2016/02/05 00:32:32]

It's used indirectly via the #include "content/common/input_messages.h" below. 
That file declares a bunch of messages, which will then be instantiated using
this IPC_MESSAGE_DECL macro definition instead, which is how they implement
GetInputMessageTypeName's switch statement.

+  case name::ID:                    \
+    return #name;
 
 const char* GetInputMessageTypeName(const IPC::Message& message) {
   switch (message.type()) {
 #include "content/common/input_messages.h"
     default:
       NOTREACHED() << "Invalid message type: " << message.type();
       break;
   };
   return "NonInputMsgType";
 }
@@ skipping 156 matching lines @@
 void InputEventFilter::SendMessageOnIOThread(scoped_ptr<IPC::Message> message) {
   DCHECK(io_task_runner_->BelongsToCurrentThread());
 
   if (!sender_)
     return;  // Filter was removed.
 
   sender_->Send(message.release());
 }
 
 }  // namespace content