Add support for enabling DCHECKs in release mode

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 @@
 
 // mark-compact.cc
 DEFINE_BOOL(force_marking_deque_overflows, false,
             "force overflows of marking deque by reducing it's size "
             "to 64 words")
 
 DEFINE_BOOL(stress_compaction, false,
             "stress the GC compactor to flush out bugs (implies "
             "--force_marking_deque_overflows)")
 
+// checks.cc
+#ifdef ENABLE_SLOW_DCHECKS
+DEFINE_BOOL(enable_slow_asserts, false,
+            "enable asserts that are slow to execute")
+#endif
+
 //
 // Debug only flags
 //
 #undef FLAG
 #ifdef DEBUG
 #define FLAG FLAG_FULL
 #else
 #define FLAG FLAG_READONLY
 #endif
 
-// checks.cc
-#ifdef ENABLE_SLOW_DCHECKS
-DEFINE_BOOL(enable_slow_asserts, false,
-            "enable asserts that are slow to execute")
-#endif
-
 // codegen-ia32.cc / codegen-arm.cc / macro-assembler-*.cc
 DEFINE_BOOL(print_source, false, "pretty print source code")
 DEFINE_BOOL(print_builtin_source, false,
             "pretty print source code for builtins")
 DEFINE_BOOL(print_ast, false, "print source AST")
 DEFINE_BOOL(print_builtin_ast, false, "print source AST for builtins")
 DEFINE_STRING(stop_at, "", "function name where to insert a breakpoint")
 DEFINE_BOOL(trap_on_abort, false, "replace aborts by breakpoints")
 
 // compiler.cc
@@ skipping 207 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