Oilpan: Schedule a precise GC when a page navigates

Source/platform/heap/ThreadState.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
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 #endif
 
     void didV8MajorGC();
 
     void performIdleGC(double deadlineSeconds);
     void performIdleLazySweep(double deadlineSeconds);
 
     void scheduleIdleGC();
     void scheduleIdleLazySweep();
     void schedulePreciseGC();
+    // estimatedRemovalRatio is the estimated ratio of objects that will be no
+    // longer necessary due to the navigation.
+    bool shouldSchedulePreciseGCOnNavigation(float estimatedRemovalRatio);
     void scheduleGCIfNeeded();
     void setGCState(GCState);
     GCState gcState() const;
     bool isInGC() const { return gcState() == GCRunning; }
     bool isSweepingInProgress() const
     {
         return gcState() == Sweeping || gcState() == SweepingAndPreciseGCScheduled || gcState() == SweepingAndIdleGCScheduled;
     }
 
     // A GC runs in the following sequence.
@@ skipping 460 matching lines @@
 };
 
 template<> class ThreadStateFor<AnyThread> {
 public:
     static ThreadState* state() { return ThreadState::current(); }
 };
 
 } // namespace blink
 
 #endif // ThreadState_h