Make IPC::Channel::Listener:OnMessageReceived have a return value indicating ...

ppapi/proxy/ppp_instance_proxy.cc

Index: ppapi/proxy/ppp_instance_proxy.cc
===================================================================
--- ppapi/proxy/ppp_instance_proxy.cc	(revision 70108)
+++ ppapi/proxy/ppp_instance_proxy.cc	(working copy)
@@ -109,7 +109,8 @@
   return INTERFACE_ID_PPP_INSTANCE;
 }
 
-void PPP_Instance_Proxy::OnMessageReceived(const IPC::Message& msg) {
+bool PPP_Instance_Proxy::OnMessageReceived(const IPC::Message& msg) {
+  bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(PPP_Instance_Proxy, msg)
     IPC_MESSAGE_HANDLER(PpapiMsg_PPPInstance_DidCreate,
                         OnMsgDidCreate)
@@ -125,7 +126,9 @@
                         OnMsgHandleDocumentLoad)
     IPC_MESSAGE_HANDLER(PpapiMsg_PPPInstance_GetInstanceObject,
                         OnMsgGetInstanceObject)
+    IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
+  return handled;
 }
 
 void PPP_Instance_Proxy::OnMsgDidCreate(