Introduce a flag for tracing retaining path in GC.

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 599 matching lines @@
             "old code (required for code flushing)")
 DEFINE_BOOL(incremental_marking, true, "use incremental marking")
 DEFINE_BOOL(incremental_marking_steps, true, "do incremental marking steps")
 DEFINE_BOOL(concurrent_sweeping, true, "use concurrent sweeping")
 DEFINE_BOOL(trace_incremental_marking, false,
             "trace progress of the incremental marking")
 DEFINE_BOOL(track_gc_object_stats, false,
             "track object counts and memory usage")
 DEFINE_BOOL(track_detached_contexts, false,
             "track native contexts that are expected to be garbage collected")
+#ifdef TRACE_RETAINING_PATH
+DEFINE_STRING(
+    trace_retaining_path_for, "",
+    "trace retaining paths for all JS objects with this constructor name")
+#endif
 #ifdef VERIFY_HEAP
 DEFINE_BOOL(verify_heap, false, "verify heap pointers before and after GC")
 #endif
 
 
 // heap-snapshot-generator.cc
 DEFINE_BOOL(heap_profiler_trace_objects, false,
             "Dump heap object allocations/movements/size_updates")
 
 
@@ skipping 386 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