Add ScopedForbidReturn and its test

util/misc/scoped_forbid_return.h

Index: util/misc/scoped_forbid_return.h
diff --git a/util/misc/scoped_forbid_return.h b/util/misc/scoped_forbid_return.h
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+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef CRASHPAD_UTIL_MISC_SCOPED_FORBID_RETURN_H_
+#define CRASHPAD_UTIL_MISC_SCOPED_FORBID_RETURN_H_
+
+#include "base/basictypes.h"
+
+namespace crashpad {
+
+//! \brief Asserts that a scope must not be exited while unsafe.
+//!
+//! An object of this class has two states: armed and disarmed. A disarmed
+//! object is a harmless no-op. An armed object will abort execution upon
+//! destruction. Newly-constructed objects are armed by default.
+//!
+//! These objects may be used to assert that a scope not be exited while it is
+//! unsafe to do so. If it ever becomes safe to leave such a scope, an object
+//! can be disarmed.
+class ScopedForbidReturn {
+ public:
+  ScopedForbidReturn() : armed_(true) {}
+  ~ScopedForbidReturn();
+
+  //! \brief Arms the object so that it will abort execution when destroyed.
+  //!
+  //! The most recent call to Arm() or Disarm() sets the state of the object.
+  void Arm() { armed_ = true; }
+
+  //! \brief Arms the object so that it will abort execution when destroyed.
+  //!
+  //! The most recent call to Arm() or Disarm() sets the state of the object.
+  void Disarm() { armed_ = false; }
+
+ private:
+  bool armed_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedForbidReturn);
+};
+
+}  // namespace crashpad
+
+#endif  // CRASHPAD_UTIL_MISC_SCOPED_FORBID_RETURN_H_