Oilpan: Discard unused system pages when sweeping NormalPageHeaps

third_party/WebKit/Source/platform/heap/Heap.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 248 matching lines @@
     static void decreaseWrapperCount(size_t delta) { atomicSubtract(&s_wrapperCount, static_cast<long>(delta)); }
     static size_t wrapperCount() { return acquireLoad(&s_wrapperCount); }
     static size_t wrapperCountAtLastGC() { return acquireLoad(&s_wrapperCountAtLastGC); }
     static void increaseCollectedWrapperCount(size_t delta) { atomicAdd(&s_collectedWrapperCount, static_cast<long>(delta)); }
     static size_t collectedWrapperCount() { return acquireLoad(&s_collectedWrapperCount); }
     static size_t partitionAllocSizeAtLastGC() { return acquireLoad(&s_partitionAllocSizeAtLastGC); }
 
     static double estimatedMarkingTime();
     static void reportMemoryUsageHistogram();
     static void reportMemoryUsageForTracing();
+    static bool isLowEndDevice() { return s_isLowEndDevice; }
 
 #if ENABLE(ASSERT)
     static uint16_t gcGeneration() { return s_gcGeneration; }
 #endif
 
 private:
     // Reset counters that track live and allocated-since-last-GC sizes.
     static void resetHeapCounters();
 
     static int heapIndexForObjectSize(size_t);
@@ skipping 11 matching lines @@
     static size_t s_allocatedSpace;
     static size_t s_allocatedObjectSize;
     static size_t s_objectSizeAtLastGC;
     static size_t s_markedObjectSize;
     static size_t s_markedObjectSizeAtLastCompleteSweep;
     static size_t s_wrapperCount;
     static size_t s_wrapperCountAtLastGC;
     static size_t s_collectedWrapperCount;
     static size_t s_partitionAllocSizeAtLastGC;
     static double s_estimatedMarkingTimePerByte;
+    static bool s_isLowEndDevice;
 #if ENABLE(ASSERT)
     static uint16_t s_gcGeneration;
 #endif
 
     friend class ThreadState;
 };
 
 template<typename T>
 struct IsEagerlyFinalizedType {
     STATIC_ONLY(IsEagerlyFinalizedType);
@@ skipping 184 matching lines @@
 void VisitorHelper<Derived>::handleWeakCell(Visitor* self, void* object)
 {
     T** cell = reinterpret_cast<T**>(object);
     if (*cell && !ObjectAliveTrait<T>::isHeapObjectAlive(*cell))
         *cell = nullptr;
 }
 
 } // namespace blink
 
 #endif // Heap_h