[heap] Remove remaining parts of PathTracer.

This should have been removed with 9e187e.

BUG=

Review-Url: https://codereview.chromium.org/2719013002
Cr-Commit-Position: refs/heads/master@{#43444}

src/heap/heap.h

@@ -2563,65 +2563,6 @@ class WeakObjectRetainer {
   virtual Object* RetainAs(Object* object) = 0;
 };
 
-
-#ifdef DEBUG
-// Helper class for tracing paths to a search target Object from all roots.
-// The TracePathFrom() method can be used to trace paths from a specific
-// object to the search target object.
-class PathTracer : public ObjectVisitor {
- public:
-  enum WhatToFind {
-    FIND_ALL,   // Will find all matches.
-    FIND_FIRST  // Will stop the search after first match.
-  };
-
-  // Tags 0, 1, and 3 are used. Use 2 for marking visited HeapObject.
-  static const int kMarkTag = 2;
-
-  // For the WhatToFind arg, if FIND_FIRST is specified, tracing will stop
-  // after the first match.  If FIND_ALL is specified, then tracing will be
-  // done for all matches.
-  PathTracer(Object* search_target, WhatToFind what_to_find,
-             VisitMode visit_mode)
-      : search_target_(search_target),
-        found_target_(false),
-        found_target_in_trace_(false),
-        what_to_find_(what_to_find),
-        visit_mode_(visit_mode),
-        object_stack_(20),
-        no_allocation() {}
-
-  void VisitPointers(Object** start, Object** end) override;
-
-  void Reset();
-  void TracePathFrom(Object** root);
-
-  bool found() const { return found_target_; }
-
-  static Object* const kAnyGlobalObject;
-
- protected:
-  class MarkVisitor;
-  class UnmarkVisitor;
-
-  void MarkRecursively(Object** p, MarkVisitor* mark_visitor);
-  void UnmarkRecursively(Object** p, UnmarkVisitor* unmark_visitor);
-  virtual void ProcessResults();
-
-  Object* search_target_;
-  bool found_target_;
-  bool found_target_in_trace_;
-  WhatToFind what_to_find_;
-  VisitMode visit_mode_;
-  List<Object*> object_stack_;
-
-  DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
-
- private:
-  DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
-};
-#endif  // DEBUG
-
 // -----------------------------------------------------------------------------
 // Allows observation of allocations.
 class AllocationObserver {

src/objects-inl.h

@@ -1457,14 +1457,7 @@ Isolate* HeapObject::GetIsolate() const {
 
 
 Map* HeapObject::map() const {
-#ifdef DEBUG
-  // Clear mark potentially added by PathTracer.
-  uintptr_t raw_value =
-      map_word().ToRawValue() & ~static_cast<uintptr_t>(PathTracer::kMarkTag);
-  return MapWord::FromRawValue(raw_value).ToMap();
-#else
   return map_word().ToMap();
-#endif
 }