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diff --git a/security/sandbox/chromium/base/threading/thread_collision_warner.h b/security/sandbox/chromium/base/threading/thread_collision_warner.h
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+++ b/security/sandbox/chromium/base/threading/thread_collision_warner.h
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+// 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.
+
+#ifndef BASE_THREADING_THREAD_COLLISION_WARNER_H_
+#define BASE_THREADING_THREAD_COLLISION_WARNER_H_
+
+#include <memory>
+
+#include "base/atomicops.h"
+#include "base/base_export.h"
+#include "base/compiler_specific.h"
+#include "base/macros.h"
+
+// A helper class alongside macros to be used to verify assumptions about thread
+// safety of a class.
+//
+// Example: Queue implementation non thread-safe but still usable if clients
+//          are synchronized somehow.
+//
+//          In this case the macro DFAKE_SCOPED_LOCK has to be
+//          used, it checks that if a thread is inside the push/pop then
+//          noone else is still inside the pop/push
+//
+// class NonThreadSafeQueue {
+//  public:
+//   ...
+//   void push(int) { DFAKE_SCOPED_LOCK(push_pop_); ... }
+//   int pop() { DFAKE_SCOPED_LOCK(push_pop_); ... }
+//   ...
+//  private:
+//   DFAKE_MUTEX(push_pop_);
+// };
+//
+//
+// Example: Queue implementation non thread-safe but still usable if clients
+//          are synchronized somehow, it calls a method to "protect" from
+//          a "protected" method
+//
+//          In this case the macro DFAKE_SCOPED_RECURSIVE_LOCK
+//          has to be used, it checks that if a thread is inside the push/pop
+//          then noone else is still inside the pop/push
+//
+// class NonThreadSafeQueue {
+//  public:
+//   void push(int) {
+//     DFAKE_SCOPED_LOCK(push_pop_);
+//     ...
+//   }
+//   int pop() {
+//     DFAKE_SCOPED_RECURSIVE_LOCK(push_pop_);
+//     bar();
+//     ...
+//   }
+//   void bar() { DFAKE_SCOPED_RECURSIVE_LOCK(push_pop_); ... }
+//   ...
+//  private:
+//   DFAKE_MUTEX(push_pop_);
+// };
+//
+//
+// Example: Queue implementation not usable even if clients are synchronized,
+//          so only one thread in the class life cycle can use the two members
+//          push/pop.
+//
+//          In this case the macro DFAKE_SCOPED_LOCK_THREAD_LOCKED pins the
+//          specified
+//          critical section the first time a thread enters push or pop, from
+//          that time on only that thread is allowed to execute push or pop.
+//
+// class NonThreadSafeQueue {
+//  public:
+//   ...
+//   void push(int) { DFAKE_SCOPED_LOCK_THREAD_LOCKED(push_pop_); ... }
+//   int pop() { DFAKE_SCOPED_LOCK_THREAD_LOCKED(push_pop_); ... }
+//   ...
+//  private:
+//   DFAKE_MUTEX(push_pop_);
+// };
+//
+//
+// Example: Class that has to be contructed/destroyed on same thread, it has
+//          a "shareable" method (with external synchronization) and a not
+//          shareable method (even with external synchronization).
+//
+//          In this case 3 Critical sections have to be defined
+//
+// class ExoticClass {
+//  public:
+//   ExoticClass() { DFAKE_SCOPED_LOCK_THREAD_LOCKED(ctor_dtor_); ... }
+//   ~ExoticClass() { DFAKE_SCOPED_LOCK_THREAD_LOCKED(ctor_dtor_); ... }
+//
+//   void Shareable() { DFAKE_SCOPED_LOCK(shareable_section_); ... }
+//   void NotShareable() { DFAKE_SCOPED_LOCK_THREAD_LOCKED(ctor_dtor_); ... }
+//   ...
+//  private:
+//   DFAKE_MUTEX(ctor_dtor_);
+//   DFAKE_MUTEX(shareable_section_);
+// };
+
+
+#if !defined(NDEBUG)
+
+#define DFAKE_UNIQUE_VARIABLE_CONCAT(a, b) a##b
+// CONCAT1 provides extra level of indirection so that __LINE__ macro expands.
+#define DFAKE_UNIQUE_VARIABLE_CONCAT1(a, b) DFAKE_UNIQUE_VARIABLE_CONCAT(a, b)
+#define DFAKE_UNIQUE_VARIABLE_NAME(a) DFAKE_UNIQUE_VARIABLE_CONCAT1(a, __LINE__)
+
+// Defines a class member that acts like a mutex. It is used only as a
+// verification tool.
+#define DFAKE_MUTEX(obj) \
+     mutable base::ThreadCollisionWarner obj
+// Asserts the call is never called simultaneously in two threads. Used at
+// member function scope.
+#define DFAKE_SCOPED_LOCK(obj)                                         \
+  base::ThreadCollisionWarner::ScopedCheck DFAKE_UNIQUE_VARIABLE_NAME( \
+      s_check_)(&obj)
+// Asserts the call is never called simultaneously in two threads. Used at
+// member function scope. Same as DFAKE_SCOPED_LOCK but allows recursive locks.
+#define DFAKE_SCOPED_RECURSIVE_LOCK(obj)            \
+  base::ThreadCollisionWarner::ScopedRecursiveCheck \
+      DFAKE_UNIQUE_VARIABLE_NAME(sr_check)(&obj)
+// Asserts the code is always executed in the same thread.
+#define DFAKE_SCOPED_LOCK_THREAD_LOCKED(obj) \
+  base::ThreadCollisionWarner::Check DFAKE_UNIQUE_VARIABLE_NAME(check_)(&obj)
+
+#else
+
+#define DFAKE_MUTEX(obj) typedef void InternalFakeMutexType##obj
+#define DFAKE_SCOPED_LOCK(obj) ((void)0)
+#define DFAKE_SCOPED_RECURSIVE_LOCK(obj) ((void)0)
+#define DFAKE_SCOPED_LOCK_THREAD_LOCKED(obj) ((void)0)
+
+#endif
+
+namespace base {
+
+// The class ThreadCollisionWarner uses an Asserter to notify the collision
+// AsserterBase is the interfaces and DCheckAsserter is the default asserter
+// used. During the unit tests is used another class that doesn't "DCHECK"
+// in case of collision (check thread_collision_warner_unittests.cc)
+struct BASE_EXPORT AsserterBase {
+  virtual ~AsserterBase() = default;
+  virtual void warn() = 0;
+};
+
+struct BASE_EXPORT DCheckAsserter : public AsserterBase {
+  ~DCheckAsserter() override = default;
+  void warn() override;
+};
+
+class BASE_EXPORT ThreadCollisionWarner {
+ public:
+  // The parameter asserter is there only for test purpose
+  explicit ThreadCollisionWarner(AsserterBase* asserter = new DCheckAsserter())
+      : valid_thread_id_(0),
+        counter_(0),
+        asserter_(asserter) {}
+
+  ~ThreadCollisionWarner() {
+    delete asserter_;
+  }
+
+  // This class is meant to be used through the macro
+  // DFAKE_SCOPED_LOCK_THREAD_LOCKED
+  // it doesn't leave the critical section, as opposed to ScopedCheck,
+  // because the critical section being pinned is allowed to be used only
+  // from one thread
+  class BASE_EXPORT Check {
+   public:
+    explicit Check(ThreadCollisionWarner* warner)
+        : warner_(warner) {
+      warner_->EnterSelf();
+    }
+
+    ~Check() = default;
+
+   private:
+    ThreadCollisionWarner* warner_;
+
+    DISALLOW_COPY_AND_ASSIGN(Check);
+  };
+
+  // This class is meant to be used through the macro
+  // DFAKE_SCOPED_LOCK
+  class BASE_EXPORT ScopedCheck {
+   public:
+    explicit ScopedCheck(ThreadCollisionWarner* warner)
+        : warner_(warner) {
+      warner_->Enter();
+    }
+
+    ~ScopedCheck() {
+      warner_->Leave();
+    }
+
+   private:
+    ThreadCollisionWarner* warner_;
+
+    DISALLOW_COPY_AND_ASSIGN(ScopedCheck);
+  };
+
+  // This class is meant to be used through the macro
+  // DFAKE_SCOPED_RECURSIVE_LOCK
+  class BASE_EXPORT ScopedRecursiveCheck {
+   public:
+    explicit ScopedRecursiveCheck(ThreadCollisionWarner* warner)
+        : warner_(warner) {
+      warner_->EnterSelf();
+    }
+
+    ~ScopedRecursiveCheck() {
+      warner_->Leave();
+    }
+
+   private:
+    ThreadCollisionWarner* warner_;
+
+    DISALLOW_COPY_AND_ASSIGN(ScopedRecursiveCheck);
+  };
+
+ private:
+  // This method stores the current thread identifier and does a DCHECK
+  // if a another thread has already done it, it is safe if same thread
+  // calls this multiple time (recursion allowed).
+  void EnterSelf();
+
+  // Same as EnterSelf but recursion is not allowed.
+  void Enter();
+
+  // Removes the thread_id stored in order to allow other threads to
+  // call EnterSelf or Enter.
+  void Leave();
+
+  // This stores the thread id that is inside the critical section, if the
+  // value is 0 then no thread is inside.
+  volatile subtle::Atomic32 valid_thread_id_;
+
+  // Counter to trace how many time a critical section was "pinned"
+  // (when allowed) in order to unpin it when counter_ reaches 0.
+  volatile subtle::Atomic32 counter_;
+
+  // Here only for class unit tests purpose, during the test I need to not
+  // DCHECK but notify the collision with something else.
+  AsserterBase* asserter_;
+
+  DISALLOW_COPY_AND_ASSIGN(ThreadCollisionWarner);
+};
+
+}  // namespace base
+
+#endif  // BASE_THREADING_THREAD_COLLISION_WARNER_H_