[heap] 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 97f9de996f6cc8abd753072b4c003ac36bb4add9..7715734c90aea3abd743228e4d9f547b3208703b 100644
--- a/src/heap/spaces.h
+++ b/src/heap/spaces.h
@@ -622,6 +622,7 @@ class MemoryChunk {
   }
 
   size_t size() const { return size_; }
+  void set_size(size_t size) { size_ = size; }
 
   inline Heap* heap() const { return heap_; }
 
@@ -654,7 +655,7 @@ 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(); }
 
@@ -992,6 +993,10 @@ 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();
+
   // 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
@@ -1443,6 +1448,7 @@ 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
@@ -1494,6 +1500,9 @@ class MemoryAllocator {
   // FreeMemory can be called concurrently when PreFree was executed before.
   void PerformFreeMemory(MemoryChunk* chunk);
 
+  void PartialFreeMemory(base::VirtualMemory* reservation,
+                         Executability executable, Address free_start);
+
   // See AllocatePage for public interface. Note that currently we only support
   // pools for NOT_EXECUTABLE pages of size MemoryChunk::kPageSize.
   template <typename SpaceType>