[crankshaft] Replace stub cache harvesting with a bit of type propagation

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 314 matching lines @@
             "eliminate write barriers targeting allocations in optimized code")
 DEFINE_INT(max_inlining_levels, 5, "maximum number of inlining levels")
 DEFINE_INT(max_inlined_source_size, 600,
            "maximum source size in bytes considered for a single inlining")
 DEFINE_INT(max_inlined_nodes, 196,
            "maximum number of AST nodes considered for a single inlining")
 DEFINE_INT(max_inlined_nodes_cumulative, 400,
            "maximum cumulative number of AST nodes considered for inlining")
 DEFINE_BOOL(loop_invariant_code_motion, true, "loop invariant code motion")
 DEFINE_BOOL(fast_math, true, "faster (but maybe less accurate) math functions")
-DEFINE_BOOL(collect_megamorphic_maps_from_stub_cache, true,
+DEFINE_BOOL(collect_megamorphic_maps_from_stub_cache, false,
             "crankshaft harvests type feedback from stub cache")
 DEFINE_BOOL(hydrogen_stats, false, "print statistics for hydrogen")
 DEFINE_BOOL(trace_check_elimination, false, "trace check elimination phase")
 DEFINE_BOOL(trace_environment_liveness, false,
             "trace liveness of local variable slots")
 DEFINE_BOOL(trace_hydrogen, false, "trace generated hydrogen to file")
 DEFINE_STRING(trace_hydrogen_filter, "*", "hydrogen tracing filter")
 DEFINE_BOOL(trace_hydrogen_stubs, false, "trace generated hydrogen for stubs")
 DEFINE_STRING(trace_hydrogen_file, NULL, "trace hydrogen to given file name")
 DEFINE_STRING(trace_phase, "HLZ", "trace generated IR for specified phases")
@@ skipping 806 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