Add flags to force or prevent setting of isolate.is_memory_constrained.

src/flag-definitions.h

 // 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 130 matching lines @@
 #else
 # define ENABLE_ARMV7_DEFAULT false
 #endif
 #if (defined CAN_USE_VFP32DREGS) || !(defined ARM_TEST)
 # define ENABLE_32DREGS_DEFAULT true
 #else
 # define ENABLE_32DREGS_DEFAULT false
 #endif
 
 #define DEFINE_bool(nam, def, cmt)   FLAG(BOOL, bool, nam, def, cmt)
+#define DEFINE_maybe_bool(nam, cmt)  FLAG(MAYBE_BOOL, Maybe<bool>, nam,  \
+                                          Maybe<bool>(), cmt)
 #define DEFINE_int(nam, def, cmt)    FLAG(INT, int, nam, def, cmt)
 #define DEFINE_float(nam, def, cmt)  FLAG(FLOAT, double, nam, def, cmt)
 #define DEFINE_string(nam, def, cmt) FLAG(STRING, const char*, nam, def, cmt)
 #define DEFINE_args(nam, def, cmt)   FLAG(ARGS, JSArguments, nam, def, cmt)
 
 #define DEFINE_ALIAS_bool(alias, nam)  FLAG_ALIAS(BOOL, bool, alias, nam)
 #define DEFINE_ALIAS_int(alias, nam)   FLAG_ALIAS(INT, int, alias, nam)
 #define DEFINE_ALIAS_float(alias, nam) FLAG_ALIAS(FLOAT, double, alias, nam)
 #define DEFINE_ALIAS_string(alias, nam) \
   FLAG_ALIAS(STRING, const char*, alias, nam)
@@ skipping 432 matching lines @@
 DEFINE_bool(preallocate_message_memory, false,
             "preallocate some memory to build stack traces.")
 DEFINE_bool(randomize_hashes,
             true,
             "randomize hashes to avoid predictable hash collisions "
             "(with snapshots this option cannot override the baked-in seed)")
 DEFINE_int(hash_seed,
            0,
            "Fixed seed to use to hash property keys (0 means random)"
            "(with snapshots this option cannot override the baked-in seed)")
+DEFINE_maybe_bool(force_memory_constrained,
+           "force (if true) or prevent (if false) the runtime from treating "
+           "the device as being memory constrained.")
 
 // v8.cc
 DEFINE_bool(preemption, false,
             "activate a 100ms timer that switches between V8 threads")
 
 // Regexp
 DEFINE_bool(regexp_optimization, true, "generate optimized regexp code")
 
 // 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")
 #else
 DEFINE_string(testing_serialization_file, "/tmp/serdes",
               "file in which to serialize heap")
@@ skipping 204 matching lines @@
 #endif
 #endif
 
 // Cleanup...
 #undef FLAG_FULL
 #undef FLAG_READONLY
 #undef FLAG
 #undef FLAG_ALIAS
 
 #undef DEFINE_bool
+#undef DEFINE_maybe_bool
 #undef DEFINE_int
 #undef DEFINE_string
 #undef DEFINE_float
 #undef DEFINE_args
 #undef DEFINE_implication
 #undef DEFINE_ALIAS_bool
 #undef DEFINE_ALIAS_int
 #undef DEFINE_ALIAS_string
 #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