Retire StringTracker.

src/api.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.
 
 #ifndef V8_API_H_
 #define V8_API_H_
 
 #include "src/v8.h"
 
 #include "include/v8-testing.h"
@@ skipping 388 matching lines @@
   }
 
 OPEN_HANDLE_LIST(MAKE_OPEN_HANDLE)
 
 #undef MAKE_OPEN_HANDLE
 #undef OPEN_HANDLE_LIST
 
 
 namespace internal {
 
-// Tracks string usage to help make better decisions when
-// externalizing strings.
-//
-// Implementation note: internally this class only tracks fresh
-// strings and keeps a single use counter for them.
-class StringTracker {
- public:
-  // Records that the given string's characters were copied to some
-  // external buffer. If this happens often we should honor
-  // externalization requests for the string.
-  void RecordWrite(Handle<String> string) {
-    Address address = reinterpret_cast<Address>(*string);
-    Address top = isolate_->heap()->NewSpaceTop();
-    if (IsFreshString(address, top)) {
-      IncrementUseCount(top);
-    }
-  }
-
-  // Estimates freshness and use frequency of the given string based
-  // on how close it is to the new space top and the recorded usage
-  // history.
-  inline bool IsFreshUnusedString(Handle<String> string) {
-    Address address = reinterpret_cast<Address>(*string);
-    Address top = isolate_->heap()->NewSpaceTop();
-    return IsFreshString(address, top) && IsUseCountLow(top);
-  }
-
- private:
-  StringTracker() : use_count_(0), last_top_(NULL), isolate_(NULL) { }
-
-  static inline bool IsFreshString(Address string, Address top) {
-    return top - kFreshnessLimit <= string && string <= top;
-  }
-
-  inline bool IsUseCountLow(Address top) {
-    if (last_top_ != top) return true;
-    return use_count_ < kUseLimit;
-  }
-
-  inline void IncrementUseCount(Address top) {
-    if (last_top_ != top) {
-      use_count_ = 0;
-      last_top_ = top;
-    }
-    ++use_count_;
-  }
-
-  // Single use counter shared by all fresh strings.
-  int use_count_;
-
-  // Last new space top when the use count above was valid.
-  Address last_top_;
-
-  Isolate* isolate_;
-
-  // How close to the new space top a fresh string has to be.
-  static const int kFreshnessLimit = 1024;
-
-  // The number of uses required to consider a string useful.
-  static const int kUseLimit = 32;
-
-  friend class Isolate;
-
-  DISALLOW_COPY_AND_ASSIGN(StringTracker);
-};
-
 
 class DeferredHandles {
  public:
   ~DeferredHandles();
 
  private:
   DeferredHandles(Object** first_block_limit, Isolate* isolate)
       : next_(NULL),
         previous_(NULL),
         first_block_limit_(first_block_limit),
@@ skipping 220 matching lines @@
     stress_type_ = stress_type;
   }
 
  private:
   static v8::Testing::StressType stress_type_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_API_H_