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

chrome/browser/extensions/api/alarms/alarms_api_unittest.cc

Index: chrome/browser/extensions/api/alarms/alarms_api_unittest.cc
===================================================================
--- chrome/browser/extensions/api/alarms/alarms_api_unittest.cc	(revision 270218)
+++ chrome/browser/extensions/api/alarms/alarms_api_unittest.cc	(working copy)
@@ -283,9 +283,10 @@
   const IPC::Message* warning = sink.GetUniqueMessageMatching(
       ExtensionMsg_AddMessageToConsole::ID);
   ASSERT_TRUE(warning);
-  content::ConsoleMessageLevel level = content::CONSOLE_MESSAGE_LEVEL_DEBUG;
-  std::string message;
-  ExtensionMsg_AddMessageToConsole::Read(warning, &level, &message);
+  ExtensionMsg_AddMessageToConsole::Param params;
+  ExtensionMsg_AddMessageToConsole::Read(warning, &params);
+  content::ConsoleMessageLevel level = params.a;
+  std::string message = params.b;
   EXPECT_EQ(content::CONSOLE_MESSAGE_LEVEL_WARNING, level);
   EXPECT_THAT(message, testing::HasSubstr("delay is less than minimum of 1"));
 }