mac: Add CrashpadClient::UseSystemDefaultHandler()

util/mach/mach_extensions.h

 // 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,
@@ skipping 97 matching lines @@
 //! `EXC_MASK_ALL`, and thus ExcMaskAll(), never includes the value of
 //! `EXC_MASK_CRASH` or `EXC_MASK_CORPSE_NOTIFY`. For situations where an
 //! exception mask corresponding to every possible exception understood by the
 //! running kernel is desired, use this function instead.
 //!
 //! Should new exception types be introduced in the future, this function will
 //! be updated to include their bits in the returned mask value when run time
 //! support is present.
 exception_mask_t ExcMaskValid();
 
+//! \brief Obtains the system’s default Mach exception handler for crash-type
+//!     exceptions.
+//!
+//! This is obtained by looking up `"com.apple.ReportCrash"` with the bootstrap
+//! server. The service name comes from the first launch agent loaded by
+//! `launchd` with a `MachServices` entry having `ExceptionServer` set. This
+//! launch agent is normally loaded from
+//! `/System/Library/LaunchAgents/com.apple.ReportCrash.plist`.
+//!
+//! \return On success, a send right to a Mach exception handler corresponding
+//!     to the system’s default crash reporter. On failure, `MACH_PORT_NULL`,
+//!     with a message logged.
+exception_handler_t SystemCrashReporterHandler();

[Robert Sesek, 2015/10/02 18:30:19]

I think this could return a ScopedMachSendRight, since ScopedGeneric now has
move support.

+
 }  // namespace crashpad
 
 #endif  // CRASHPAD_UTIL_MACH_MACH_EXTENSIONS_H_