Don't run the second pass of the pending phantom callbacks if the heap has been torn down.

tools/gyp/v8.gyp

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 406 matching lines @@
         '../../src/bignum.h',
         '../../src/bit-vector.cc',
         '../../src/bit-vector.h',
         '../../src/bootstrapper.cc',
         '../../src/bootstrapper.h',
         '../../src/builtins.cc',
         '../../src/builtins.h',
         '../../src/bytecodes-irregexp.h',
         '../../src/cached-powers.cc',
         '../../src/cached-powers.h',
+        '../../src/cancelable-task.cc',
+        '../../src/cancelable-task.h',
         '../../src/char-predicates.cc',
         '../../src/char-predicates-inl.h',
         '../../src/char-predicates.h',
         '../../src/checks.cc',
         '../../src/checks.h',
         '../../src/circular-queue-inl.h',
         '../../src/circular-queue.h',
         '../../src/code-factory.cc',
         '../../src/code-factory.h',
         '../../src/code-stubs.cc',
@@ skipping 1529 matching lines @@
         }],
         ['want_separate_host_toolset==1', {
           'toolsets': ['host'],
         }, {
           'toolsets': ['target'],
         }],
       ],
     },
   ],
 }