[heap] Remove js call rate heuristic from memory reducer.

src/heap/memory-reducer.h

 // Copyright 2015 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_HEAP_memory_reducer_H
 #define V8_HEAP_memory_reducer_H
 
 #include "include/v8-platform.h"
 #include "src/base/macros.h"
 #include "src/cancelable-task.h"
@@ skipping 131 matching lines @@
     // v8::internal::CancelableTask overrides.
     void RunInternal() override;
     MemoryReducer* memory_reducer_;
     DISALLOW_COPY_AND_ASSIGN(TimerTask);
   };
 
   void NotifyTimer(const Event& event);
 
   static bool WatchdogGC(const State& state, const Event& event);
 
-  // Returns the rate of JS calls initiated from the API.
-  double SampleAndGetJsCallsPerMs(double time_ms);
-
   Heap* heap_;
   State state_;
   unsigned int js_calls_counter_;
   double js_calls_sample_time_ms_;
 
   // Used in cctest.
   friend class HeapTester;
   DISALLOW_COPY_AND_ASSIGN(MemoryReducer);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_memory_reducer_H