Don't unlink evacuation candidates before sweeping, move them to the end of their list of pages.

src/spaces.h

Index: src/spaces.h
diff --git a/src/spaces.h b/src/spaces.h
index 68ce26bbd48cba4d53194ee2fab70eb7ff8ced63..d30afeeb387ee4500d0254e008e9ba98748597cc 100644
--- a/src/spaces.h
+++ b/src/spaces.h
@@ -1854,7 +1854,7 @@ class PagedSpace : public Space {
   void IncreaseCapacity(int size);
 
   // Releases an unused page and shrinks the space.
-  void ReleasePage(Page* page, bool unlink);
+  void ReleasePage(Page* page);
 
   // The dummy page that anchors the linked list of pages.
   Page* anchor() { return &anchor_; }
@@ -1920,6 +1920,14 @@ class PagedSpace : public Space {
   // It returns true when sweeping is completed and false otherwise.
   bool EnsureSweeperProgress(intptr_t size_in_bytes);
 
+  void set_end_of_unswept_pages(Page* page) {
+    end_of_unswept_pages_ = page;
+  }
+
+  Page* end_of_unswept_pages() {
+    return end_of_unswept_pages_;
+  }
+
   Page* FirstPage() { return anchor_.next_page(); }
   Page* LastPage() { return anchor_.prev_page(); }
 
@@ -1964,6 +1972,8 @@ class PagedSpace : public Space {
   // sweeping is done conservatively.
   intptr_t unswept_free_bytes_;
 
+  Page* end_of_unswept_pages_;
+
   // Expands the space by allocating a fixed number of pages. Returns false if
   // it cannot allocate requested number of pages from OS, or if the hard heap
   // size limit has been hit.