Update legacy Tuple-using code.

ppapi/proxy/plugin_var_tracker_unittest.cc

 // Copyright (c) 2012 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 "ipc/ipc_test_sink.h"
 #include "ppapi/c/dev/ppp_class_deprecated.h"
 #include "ppapi/proxy/plugin_var_tracker.h"
 #include "ppapi/proxy/ppapi_messages.h"
 #include "ppapi/proxy/ppapi_proxy_test.h"
 #include "ppapi/proxy/proxy_object_var.h"
@@ skipping 38 matching lines @@
 
  protected:
   // Asserts that there is a unique "release object" IPC message in the test
   // sink. This will return the var ID from the message or -1 if none found.
   int32 GetObjectIDForUniqueReleaseObject() {
     const IPC::Message* release_msg = sink().GetUniqueMessageMatching(
         PpapiHostMsg_PPBVar_ReleaseObject::ID);
     if (!release_msg)
       return -1;
 
-    Tuple1<int64> id;
+    Tuple<int64> id;
     PpapiHostMsg_PPBVar_ReleaseObject::Read(release_msg, &id);
-    return id.a;
+    return get<0>(id);
   }
 };
 
 TEST_F(PluginVarTrackerTest, GetHostObject) {
   ProxyAutoLock lock;
   PP_Var host_object = MakeObject(12345);
 
   // Round-trip through the tracker to make sure the host object comes out the
   // other end.
   PP_Var plugin_object = var_tracker().ReceiveObjectPassRef(
@@ skipping 167 matching lines @@
 
   // Release the plugin ref to the var. Since the instance is gone this should
   // call deallocate.
   object = NULL;
   var_tracker().ReleaseVar(plugin_var);
   EXPECT_EQ(1, deallocate_called);
 }
 
 }  // namespace proxy
 }  // namespace ppapi