Add --trace-hydrogen-filter flag.

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 238 matching lines @@
            "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,
             "crankshaft harvests type feedback from stub cache")
 DEFINE_bool(hydrogen_stats, false, "print statistics for hydrogen")
 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")
 DEFINE_bool(trace_inlining, false, "trace inlining decisions")
 DEFINE_bool(trace_alloc, false, "trace register allocator")
 DEFINE_bool(trace_all_uses, false, "trace all use positions")
 DEFINE_bool(trace_range, false, "trace range analysis")
 DEFINE_bool(trace_gvn, false, "trace global value numbering")
 DEFINE_bool(trace_representation, false, "trace representation types")
 DEFINE_bool(trace_escape_analysis, false, "trace hydrogen escape analysis")
@@ skipping 578 matching lines @@
 #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