Add a skeleton gamepad resource.

ppapi/host/dispatch_host_message.h

Index: ppapi/host/dispatch_host_message.h
diff --git a/ppapi/host/dispatch_host_message.h b/ppapi/host/dispatch_host_message.h
index 070b746b329fa96cb845350d4d25489bcbbfad43..9a3fae52e3721b59fa1c05a0e04d6ec94b26e0ee 100644
--- a/ppapi/host/dispatch_host_message.h
+++ b/ppapi/host/dispatch_host_message.h
@@ -61,20 +61,28 @@ inline int32_t DispatchResourceCall(ObjT* obj, Method method,
   return (obj->*method)(context, arg.a, arg.b, arg.c, arg.d, arg.e);
 }
 
+// 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).
 #define PPAPI_DISPATCH_HOST_RESOURCE_CALL(msg_class, member_func) \
     case msg_class::ID: { \
-        TRACK_RUN_IN_IPC_HANDLER(member_func); \
-        msg_class::Schema::Param p; \
-        if (msg_class::Read(&ipc_message__, &p)) { \
-          return ppapi::host::DispatchResourceCall( \
-              this, \
-              &_IpcMessageHandlerClass::member_func, \
-              context, p); \
-        } else { \
-          return PP_ERROR_FAILED; \
-        }  \
-      }  \
-      break;
+      TRACK_RUN_IN_IPC_HANDLER(member_func); \
+      msg_class::Schema::Param p; \
+      if (msg_class::Read(&ipc_message__, &p)) { \
+        return ppapi::host::DispatchResourceCall( \
+            this, \
+            &_IpcMessageHandlerClass::member_func, \
+            context, p); \
+      } \
+      return PP_ERROR_FAILED; \
+    }
+
+#define PPAPI_DISPATCH_HOST_RESOURCE_CALL_0(msg_class, member_func) \
+  case msg_class::ID: { \
+      TRACK_RUN_IN_IPC_HANDLER(member_func); \
+      return member_func(context); \
+    }
+
 
 }  // namespace host
 }  // namespace ppapi