[Mac] Record backtrace with nsexception logging.

chrome/common/crash_keys.h

 // Copyright (c) 2013 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 CHROME_COMMON_CRASH_KEYS_H_
 #define CHROME_COMMON_CRASH_KEYS_H_
 
 #include "base/debug/crash_logging.h"
 
 namespace crash_keys {
 
 // Registers all of the potential crash keys that can be sent to the crash
 // reporting server. Returns the size of the union of all keys.
 size_t RegisterChromeCrashKeys();
 
 // Crash Key Name Constants ////////////////////////////////////////////////////
 
 #if defined(OS_MACOSX)
 namespace mac {
 
 // Used to report the first Cocoa/Mac NSException and its backtrace.
 extern const char kFirstNSException[];
 extern const char kFirstNSExceptionTrace[];
 
 // Used to report the last Cocoa/Mac NSException and its backtrace.
 extern const char kLastNSException[];
 extern const char kLastNSExceptionTrace[];
 
-// Records the current NSException as it's being created.
+// Records the current NSException as it is being created, and its backtrace.
 extern const char kNSException[];
+extern const char kNSExceptionTrace[];
 
 // In the CrApplication, records information about the current event's
 // target-action.
 extern const char kSendAction[];
 
 // Records Cocoa zombie/used-after-freed objects that resulted in a
 // deliberate crash.
 extern const char kZombie[];
 extern const char kZombieTrace[];
 
 }  // namespace mac
 #endif
 
 }  // namespace crash_keys
 
 #endif  // CHROME_COMMON_CRASH_KEYS_H_