PPAPI: Introduce concept of ResourceHosts "pinning" each other

base/memory/linked_ptr.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.
 //
 // A "smart" pointer type with reference tracking.  Every pointer to a
 // particular object is kept on a circular linked list.  When the last pointer
 // to an object is destroyed or reassigned, the object is deleted.
 //
 // Used properly, this deletes the object when the last reference goes away.
 // There are several caveats:
@@ skipping 116 matching lines @@
   bool operator==(const T* p) const { return value_ == p; }
   bool operator!=(const T* p) const { return value_ != p; }
   template <typename U>
   bool operator==(linked_ptr<U> const& ptr) const {
     return value_ == ptr.get();
   }
   template <typename U>
   bool operator!=(linked_ptr<U> const& ptr) const {
     return value_ != ptr.get();
   }
+  // To allow use as a key in map or set.
+  bool operator<(linked_ptr<T> const& ptr) const { return value_ < ptr.get(); }
 
  private:
   template <typename U>
   friend class linked_ptr;
 
   T* value_;
   linked_ptr_internal link_;
 
   void depart() {
     if (link_.depart()) delete value_;
@@ skipping 25 matching lines @@
 
 // A function to convert T* into linked_ptr<T>
 // Doing e.g. make_linked_ptr(new FooBarBaz<type>(arg)) is a shorter notation
 // for linked_ptr<FooBarBaz<type> >(new FooBarBaz<type>(arg))
 template <typename T>
 linked_ptr<T> make_linked_ptr(T* ptr) {
   return linked_ptr<T>(ptr);
 }
 
 #endif  // BASE_MEMORY_LINKED_PTR_H_