Make InToSpace/InFromSpace use the page header.

src/spaces.cc

Index: src/spaces.cc
diff --git a/src/spaces.cc b/src/spaces.cc
index 157458d4680d2064274f730026d76c5b9e269103..5e2c56f321cfe689d0cb9607b077c5b8b72446d5 100644
--- a/src/spaces.cc
+++ b/src/spaces.cc
@@ -391,7 +391,9 @@ void Page::InitializeAsAnchor(PagedSpace* owner) {
 }
 
 
-NewSpacePage* NewSpacePage::Initialize(Heap* heap, Address start) {
+NewSpacePage* NewSpacePage::Initialize(Heap* heap,
+                                       Address start,
+                                       SemiSpaceId id) {
   MemoryChunk* chunk = MemoryChunk::Initialize(heap,
                                                start,
                                                Page::kPageSize,
@@ -399,6 +401,11 @@ NewSpacePage* NewSpacePage::Initialize(Heap* heap, Address start) {
                                                heap->new_space());
   chunk->initialize_scan_on_scavenge(true);
   chunk->SetFlag(MemoryChunk::IN_NEW_SPACE);
+  if (id == kSecondSemiSpace) {
+    chunk->SetFlag(MemoryChunk::SEMI_SPACE_TAG);
+  } else {
+    ASSERT(!chunk->IsFlagSet(MemoryChunk::SEMI_SPACE_TAG));
+  }
   heap->incremental_marking()->SetNewSpacePageFlags(chunk);
   return static_cast<NewSpacePage*>(chunk);
 }
@@ -1035,7 +1042,7 @@ bool SemiSpace::Commit() {
   committed_ = true;
   // TODO(gc): When more than one page is present, initialize and
   // chain them all.
-  current_page_ = NewSpacePage::Initialize(heap(), start_);
+  current_page_ = NewSpacePage::Initialize(heap(), start_, id_);
   return true;
 }