Add APIs to protect critical tasks on iOS.

base/critical_closure_stub.cc

Index: base/critical_closure_stub.cc
diff --git a/base/critical_closure_stub.cc b/base/critical_closure_stub.cc
new file mode 100644
index 0000000000000000000000000000000000000000..abcafdc7b4c530a11b2391177baffb5cf926d24d
--- /dev/null
+++ b/base/critical_closure_stub.cc
@@ -0,0 +1,15 @@
+// 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 "base/critical_closure.h"
+
+namespace base {
+
+base::Closure MakeCriticalClosure(const base::Closure& closure) {

[Mark Mentovai, 2012/07/31 23:16:33]

You should get rid of this stub file and write this code inline in the header
for non-iOS. There should be to be zero code size impact on other platforms.

[stuartmorgan, 2012/08/01 04:31:55]

Okay; we did it this way originally because I thought our style guide made
non-header declarations preferred even for cases like this. I guess this falls
under the "simple getter" case though (in a somewhat non-obvious way).

[Chen Yu, 2012/08/01 11:26:13]

Done.

+  // No-op for platforms where the application does not need to acquire
+  // background time for closures to finish when it goes into the background.
+  return closure;
+}
+
+}  // namespace base