Make PendingTask move-only and pass it by value on retaining params

base/stl_util.h

 // Copyright (c) 2011 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.
 
 // Derived from google3/util/gtl/stl_util.h
 
 #ifndef BASE_STL_UTIL_H_
 #define BASE_STL_UTIL_H_
 
 #include <algorithm>
@@ skipping 239 matching lines @@
 // Returns true if the sorted container |a1| contains all elements of the sorted
 // container |a2|.
 template <typename Arg1, typename Arg2>
 bool STLIncludes(const Arg1& a1, const Arg2& a2) {
   DCHECK(STLIsSorted(a1));
   DCHECK(STLIsSorted(a2));
   return std::includes(a1.begin(), a1.end(),
                        a2.begin(), a2.end());
 }
 
+// Moves out and removes the top element of a std::priority_queue.
+template <typename PriorityQueue>

[Nico, 2016/04/22 15:32:16]

this is only called from two places. the loop is in at least three. not sure if
it makes sense to put this here but don't put the other thing here

[tzik, 2016/04/25 11:36:26]

Hmm, there are several user of the pattern. And I think this is a hacky code
that should not be distributed throughout Chromium.
Anyway, let me inline this function to the caller now, and propose it
separately.

+typename PriorityQueue::value_type
+PopOutFromPriorityQueue(PriorityQueue* queue) {
+  using ValueType = typename PriorityQueue::value_type;
+  ValueType ret = std::move(const_cast<ValueType&>(queue->top()));
+  queue->pop();
+  return ret;
+}
+
 }  // namespace base
 
 #endif  // BASE_STL_UTIL_H_