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

ppapi/proxy/dispatch_reply_message.h

Index: ppapi/proxy/dispatch_reply_message.h
===================================================================
--- ppapi/proxy/dispatch_reply_message.h	(revision 270145)
+++ ppapi/proxy/dispatch_reply_message.h	(working copy)
@@ -129,6 +129,12 @@
   (obj->*method)(reply_params);
 }
 
+#define PPAPI_BEGIN_MESSAGE_MAP(class_name, msg) \
+  { \
+    typedef class_name _IpcMessageHandlerClass; \
+    const IPC::Message& ipc_message__ = msg; \
+    switch (ipc_message__.type()) { \
+
 // Note that this only works for message with 1 or more parameters. For
 // 0-parameter messages you need to use the _0 version below (since there are
 // no params in the message).
@@ -158,6 +164,10 @@
     } \
     break;
 
+#define PPAPI_END_MESSAGE_MAP() \
+  } \
+}
+
 }  // namespace proxy
 }  // namespace ppapi