[heap] Add page evacuation mode for new->new

src/heap/spaces.h

Index: src/heap/spaces.h
diff --git a/src/heap/spaces.h b/src/heap/spaces.h
index 0981c3650efe8d9b6fa6b55ac4e8b06de811e6b5..37d43b17c4c72f8ff482f6192466f6f4d16d8672 100644
--- a/src/heap/spaces.h
+++ b/src/heap/spaces.h
@@ -425,6 +425,10 @@ class MemoryChunk {
     // from new to old space during evacuation.
     PAGE_NEW_OLD_PROMOTION,
 
+    // |PAGE_NEW_NEW_PROMOTION|: A page tagged with this flag has been moved
+    // within the new space during evacuation.
+    PAGE_NEW_NEW_PROMOTION,
+
     // A black page has all mark bits set to 1 (black). A black page currently
     // cannot be iterated because it is not swept. Moreover live bytes are also
     // not updated.
@@ -2431,6 +2435,8 @@ class SemiSpace : public Space {
   // than the current capacity.
   bool ShrinkTo(int new_capacity);
 
+  bool EnsureCurrentCapacity();
+
   // Returns the start address of the first page of the space.
   Address space_start() {
     DCHECK_NE(anchor_.next_page(), anchor());
@@ -2459,7 +2465,8 @@ class SemiSpace : public Space {
   // Resets the space to using the first page.
   void Reset();
 
-  bool ReplaceWithEmptyPage(Page* page);
+  void RemovePage(Page* page);
+  void PrependPage(Page* page);
 
   // Age mark accessors.
   Address age_mark() { return age_mark_; }
@@ -2535,8 +2542,9 @@ class SemiSpace : public Space {
   Page anchor_;
   Page* current_page_;
 
-  friend class SemiSpaceIterator;
+  friend class NewSpace;
   friend class NewSpacePageIterator;
+  friend class SemiSpaceIterator;
 };
 
 
@@ -2715,12 +2723,15 @@ class NewSpace : public Space {
     return static_cast<size_t>(allocated);
   }
 
-  bool ReplaceWithEmptyPage(Page* page) {
-    // This method is called after flipping the semispace.
+  void MovePageFromSpaceToSpace(Page* page) {
     DCHECK(page->InFromSpace());
-    return from_space_.ReplaceWithEmptyPage(page);
+    from_space_.RemovePage(page);
+    to_space_.PrependPage(page);
+    pages_used_++;
   }
 
+  bool Rebalance();
+
   // Return the maximum capacity of a semispace.
   int MaximumCapacity() {
     DCHECK(to_space_.maximum_capacity() == from_space_.maximum_capacity());