Activate memory reducer for small heaps in background tabs.

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 78 matching lines @@
         : action(action),
           started_gcs(started_gcs),
           next_gc_start_ms(next_gc_start_ms),
           last_gc_time_ms(last_gc_time_ms) {}
     Action action;
     int started_gcs;
     double next_gc_start_ms;
     double last_gc_time_ms;
   };
 
-  enum EventType { kTimer, kMarkCompact, kContextDisposed };
+  enum EventType { kTimer, kMarkCompact, kPossibleGarbage };
 
   struct Event {
     EventType type;
     double time_ms;
     bool next_gc_likely_to_collect_more;
     bool should_start_incremental_gc;
     bool can_start_incremental_gc;
   };
 
   explicit MemoryReducer(Heap* heap)
       : heap_(heap),
         state_(kDone, 0, 0.0, 0.0),
         js_calls_counter_(0),
         js_calls_sample_time_ms_(0.0) {}
   // Callbacks.
   void NotifyMarkCompact(const Event& event);
-  void NotifyContextDisposed(const Event& event);
+  void NotifyPossibleGarbage(const Event& event);
   void NotifyBackgroundIdleNotification(const Event& event);
   // The step function that computes the next state from the current state and
   // the incoming event.
   static State Step(const State& state, const Event& event);
   // Posts a timer task that will call NotifyTimer after the given delay.
   void ScheduleTimer(double time_ms, double delay_ms);
   void TearDown();
   static const int kLongDelayMs;
   static const int kShortDelayMs;
   static const int kWatchdogDelayMs;
@@ skipping 31 matching lines @@
 
   // Used in cctest.
   friend class HeapTester;
   DISALLOW_COPY_AND_ASSIGN(MemoryReducer);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_memory_reducer_H