After performing scavenge, hint OS that data in from spaces are no more neede...

src/spaces-inl.h

Index: src/spaces-inl.h
===================================================================
--- src/spaces-inl.h	(revision 3342)
+++ src/spaces-inl.h	(working copy)
@@ -174,6 +174,11 @@
 // -----------------------------------------------------------------------------
 // MemoryAllocator
 
+bool MemoryAllocator::ResetBlock(Address start, size_t size,
+                                 Executability executable) {
+  return initial_chunk_->Reset(start, size, executable == EXECUTABLE);
+}
+
 bool MemoryAllocator::IsValidChunk(int chunk_id) {
   if (!IsValidChunkId(chunk_id)) return false;
 
@@ -322,6 +327,13 @@
 
 
 // -----------------------------------------------------------------------------
+// SemiSpace
+
+bool SemiSpace::Reset() {
+  return MemoryAllocator::ResetBlock(start_, capacity_, executable());
+}
+
+// -----------------------------------------------------------------------------
 // LargeObjectChunk
 
 HeapObject* LargeObjectChunk::GetObject() {