A very small marking bitmap (2 bits) is sufficient for large object page since just one object in i…

src/spaces.cc

Index: src/spaces.cc
===================================================================
--- src/spaces.cc	(revision 11322)
+++ src/spaces.cc	(working copy)
@@ -528,7 +528,12 @@
     area_start = base + CodePageAreaStartOffset();
     area_end = area_start + body_size;
   } else {
-    chunk_size = MemoryChunk::kObjectStartOffset + body_size;
+    int object_start_offset = MemoryChunk::kObjectStartOffset;
+    if (owner != NULL && owner->identity() == LO_SPACE) {
+      object_start_offset = MemoryChunk::kLargeObjectStartOffset;
+    }
+
+    chunk_size = object_start_offset + body_size;
     base = AllocateAlignedMemory(chunk_size,
                                  MemoryChunk::kAlignment,
                                  executable,
@@ -540,7 +545,7 @@
     ZapBlock(base, chunk_size);
 #endif
 
-    area_start = base + Page::kObjectStartOffset;
+    area_start = base + object_start_offset;
     area_end = base + chunk_size;
   }