Implement committed physical memory stats for Linux.

src/spaces-inl.h

Index: src/spaces-inl.h
diff --git a/src/spaces-inl.h b/src/spaces-inl.h
index c64772775aef61e3229d9faa42319d628fa6d411..8a576a83f606cf2adb314237fbbdca969742436b 100644
--- a/src/spaces-inl.h
+++ b/src/spaces-inl.h
@@ -214,6 +214,19 @@ MemoryChunk* MemoryChunk::FromAnyPointerAddress(Address addr) {
 }
 
 
+void MemoryChunk::UpdateHighWaterMark(Address mark) {
+  if (mark == NULL) return;
+  // Need to subtract one from the mark because when a chunk is full the
+  // top points to the next address after the chunk, which effectively belongs
+  // to another chunk. See the comment to Page::FromAllocationTop.
+  MemoryChunk* chunk = MemoryChunk::FromAddress(mark - 1);
+  int new_mark = static_cast<int>(mark - chunk->address());
+  if (new_mark > chunk->high_water_mark_) {
+    chunk->high_water_mark_ = new_mark;
+  }
+}
+
+
 PointerChunkIterator::PointerChunkIterator(Heap* heap)
     : state_(kOldPointerState),
       old_pointer_iterator_(heap->old_pointer_space()),