[heap] Reland uncommit unused large object page memory.

src/heap/spaces.h

Index: src/heap/spaces.h
diff --git a/src/heap/spaces.h b/src/heap/spaces.h
index e68fc8ef233b93fc06ce41a7a6613ce12dcfeae0..895722b0a30b6af50f50a1e52174f8bb7f60c24c 100644
--- a/src/heap/spaces.h
+++ b/src/heap/spaces.h
@@ -628,6 +628,7 @@ class MemoryChunk {
   }
 
   size_t size() const { return size_; }
+  void set_size(size_t size) { size_ = size; }
 
   inline Heap* heap() const { return heap_; }
 
@@ -663,7 +664,7 @@ class MemoryChunk {
   bool CommitArea(size_t requested);
 
   // Approximate amount of physical memory committed for this chunk.
-  size_t CommittedPhysicalMemory() { return high_water_mark_.Value(); }
+  size_t CommittedPhysicalMemory();
 
   Address HighWaterMark() { return address() + high_water_mark_.Value(); }
 
@@ -1003,6 +1004,12 @@ class LargePage : public MemoryChunk {
 
   inline void set_next_page(LargePage* page) { set_next_chunk(page); }
 
+  // Uncommit memory that is not in use anymore by the object. If the object
+  // cannot be shrunk 0 is returned.
+  Address GetAddressToShrink();
+
+  void ClearOutOfLiveRangeSlots(Address free_start);
+
   // A limit to guarantee that we do not overflow typed slot offset in
   // the old to old remembered set.
   // Note that this limit is higher than what assembler already imposes on
@@ -1454,6 +1461,7 @@ class MemoryAllocator {
   bool CommitMemory(Address addr, size_t size, Executability executable);
 
   void FreeMemory(base::VirtualMemory* reservation, Executability executable);
+  void PartialFreeMemory(MemoryChunk* chunk, Address start_free);
   void FreeMemory(Address addr, size_t size, Executability executable);
 
   // Commit a contiguous block of memory from the initial chunk.  Assumes that
@@ -3075,6 +3083,10 @@ class LargeObjectSpace : public Space {
   // Frees unmarked objects.
   void FreeUnmarkedObjects();
 
+  void InsertChunkMapEntries(LargePage* page);
+  void RemoveChunkMapEntries(LargePage* page);
+  void RemoveChunkMapEntries(LargePage* page, Address free_start);
+
   // Checks whether a heap object is in this space; O(1).
   bool Contains(HeapObject* obj);
   // Checks whether an address is in the object area in this space. Iterates