[Mac] Set the nsexception crash key in TERMINATING_FROM_UNCAUGHT_NSEXCEPTION().

chrome/browser/mac/exception_processor.mm

 // Copyright 2016 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.
 
 #import "chrome/browser/mac/exception_processor.h"
 
 #import <Foundation/Foundation.h>
 #include <libunwind.h>
 #include <objc/objc-exception.h>
 
@@ skipping 66 matching lines @@
 static objc_exception_preprocessor g_next_preprocessor = nullptr;
 
 static const char* const kExceptionSinkholes[] = {
   "CFRunLoopRunSpecific",
   "_dispatch_client_callout",
 };
 
 // This function is used to make it clear to the crash processor that this is
 // a forced exception crash.
 static NOINLINE void TERMINATING_FROM_UNCAUGHT_NSEXCEPTION(id exception) {
-  LOG(FATAL) << "Terminating from Objective-C exception: "
-             << base::SysNSStringToUTF8([exception name])
-             << ": " << base::SysNSStringToUTF8([exception reason]);
+  NSString* exception_message_ns = [NSString
+      stringWithFormat:@"%@: %@", [exception name], [exception reason]];
+  std::string exception_message = base::SysNSStringToUTF8(exception_message_ns);
+  base::debug::SetCrashKeyValue(crash_keys::mac::kNSException,
+                                exception_message);
+  LOG(FATAL) << "Terminating from Objective-C exception: " << exception_message;
 }
 
 static id ObjcExceptionPreprocessor(id exception) {
   static bool seen_first_exception = false;
 
   // Record UMA and crash keys about the exception.
   RecordExceptionWithUma(exception);
 
   const char* const kExceptionKey =
       seen_first_exception ? crash_keys::mac::kLastNSException
@@ skipping 68 matching lines @@
   g_next_preprocessor =
       objc_setExceptionPreprocessor(&ObjcExceptionPreprocessor);
 }
 
 void UninstallObjcExceptionPreprocessor() {
   objc_setExceptionPreprocessor(g_next_preprocessor);
   g_next_preprocessor = nullptr;
 }
 
 }  // namespace chrome