Adds a crash key to V8EventListener to help diagnose crbug.com/621730 .

blimp/engine/app/blimp_engine_crash_keys.cc

 // 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.
 
 #include "blimp/engine/app/blimp_engine_crash_keys.h"
 
 #include "base/debug/crash_logging.h"
 #include "base/macros.h"
 #include "components/crash/core/common/crash_keys.h"
 
@@ skipping 55 matching lines @@
       { "initrf_parent_process_is_live", crash_keys::kSmallSize},
       { "initrf_root_is_in_same_site_instance", crash_keys::kSmallSize},
       { "initrf_root_is_in_same_site_instance_as_parent",
         crash_keys::kSmallSize},
       { "initrf_root_process_is_live", crash_keys::kSmallSize},
       { "initrf_root_proxy_is_live", crash_keys::kSmallSize},
 
       // Temporary for https://crbug.com/612711.
       { "aci_wrong_sp_extension_id", crash_keys::kSmallSize },
 
+      // Temporary for http://crbug.com/621730.
+      { "postmessage_script_info", crash_keys::kLargeSize },
+
       // Temporary for https://crbug.com/616149.
       { "existing_extension_pref_value_type", crash_keys::kSmallSize },
     };
 
   return base::debug::InitCrashKeys(engine_keys, arraysize(engine_keys),
                                     crash_keys::kChunkMaxLength);
 }
 
 }  // namespace engine
 }  // namespace blimp