Add ScopedClosureRunner.

base/task.cc

Index: base/task.cc
diff --git a/base/task.cc b/base/task.cc
index 8c614734863fb5c8e34959dd2b00b4ac8c80e538..89d2aa80e7fbb599113e6d6efd4fe5feb9e310ae 100644
--- a/base/task.cc
+++ b/base/task.cc
@@ -34,6 +34,21 @@ Task* ScopedTaskRunner::Release() {
   return tmp;
 }
 
+ScopedClosureRunner::ScopedClosureRunner(const Closure& closure)
+    : closure_(closure) {
+}
+
+ScopedClosureRunner::~ScopedClosureRunner() {
+  if (!closure_.is_null())
+    closure_.Run();
+}
+
+Closure ScopedClosureRunner::Release() {
+  Closure result = closure_;
+  closure_.Reset();
+  return result;
+}
+
 namespace subtle {
 
 TaskClosureAdapter::TaskClosureAdapter(Task* task)