Introduce a flag to overwrite Date.now() with a fixed value

src/flag-definitions.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file defines all of the flags.  It is separated into different section,
 // for Debug, Release, Logging and Profiling, etc.  To add a new flag, find the
 // correct section, and use one of the DEFINE_ macros, without a trailing ';'.
 //
 // This include does not have a guard, because it is a template-style include,
 // which can be included multiple times in different modes.  It expects to have
@@ skipping 738 matching lines @@
 
 // snapshot-common.cc
 DEFINE_BOOL(profile_deserialization, false,
             "Print the time it takes to deserialize the snapshot.")
 DEFINE_BOOL(serialization_statistics, false,
             "Collect statistics on serialized objects.")
 
 // Regexp
 DEFINE_BOOL(regexp_optimization, true, "generate optimized regexp code")
 
+// Date
+DEFINE_INT(fixed_date, 0,
+           "Sets a fixed value for Date.now() if non-zero in seconds since the "
+           "Jan 1, 2014")
+
 // Testing flags test/cctest/test-{flags,api,serialization}.cc
 DEFINE_BOOL(testing_bool_flag, true, "testing_bool_flag")
 DEFINE_MAYBE_BOOL(testing_maybe_bool_flag, "testing_maybe_bool_flag")
 DEFINE_INT(testing_int_flag, 13, "testing_int_flag")
 DEFINE_FLOAT(testing_float_flag, 2.5, "float-flag")
 DEFINE_STRING(testing_string_flag, "Hello, world!", "string-flag")
 DEFINE_INT(testing_prng_seed, 42, "Seed used for threading test randomness")
 #ifdef _WIN32
 DEFINE_STRING(testing_serialization_file, "C:\\Windows\\Temp\\serdes",
               "file in which to testing_serialize heap")
@@ skipping 297 matching lines @@
 #undef DEFINE_ALIAS_FLOAT
 #undef DEFINE_ALIAS_ARGS
 
 #undef FLAG_MODE_DECLARE
 #undef FLAG_MODE_DEFINE
 #undef FLAG_MODE_DEFINE_DEFAULTS
 #undef FLAG_MODE_META
 #undef FLAG_MODE_DEFINE_IMPLICATIONS
 
 #undef COMMA