When compiling for-in pass correct context value to the increment instruction.

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 151 matching lines @@
 DEFINE_bool(trap_on_deopt, false, "put a break point before deoptimizing")
 DEFINE_bool(deoptimize_uncommon_cases, true, "deoptimize uncommon cases")
 DEFINE_bool(polymorphic_inlining, true, "polymorphic inlining")
 DEFINE_bool(use_osr, true, "use on-stack replacement")
 
 DEFINE_bool(trace_osr, false, "trace on-stack replacement")
 DEFINE_int(stress_runs, 0, "number of stress runs")
 DEFINE_bool(optimize_closures, true, "optimize closures")
 DEFINE_int(loop_weight, 1, "loop weight for representation inference")
 
-DEFINE_bool(optimize_for_in, false,
+DEFINE_bool(optimize_for_in, true,
             "optimize functions containing for-in loops")
 
 // Experimental profiler changes.
 DEFINE_bool(experimental_profiler, false, "enable all profiler experiments")
 DEFINE_bool(watch_ic_patching, false, "profiler considers IC stability")
 DEFINE_int(frame_count, 2, "number of stack frames inspected by the profiler")
 DEFINE_bool(self_optimization, false,
             "primitive functions trigger their own optimization")
 DEFINE_bool(count_based_interrupts, false,
             "trigger profiler ticks based on counting instead of timing")
@@ skipping 410 matching lines @@
 #undef DEFINE_bool
 #undef DEFINE_int
 #undef DEFINE_string
 #undef DEFINE_implication
 
 #undef FLAG_MODE_DECLARE
 #undef FLAG_MODE_DEFINE
 #undef FLAG_MODE_DEFINE_DEFAULTS
 #undef FLAG_MODE_META
 #undef FLAG_MODE_DEFINE_IMPLICATIONS