[heap] Move StoreBufferRebuilder into the correct header.

src/heap/store-buffer.cc

Index: src/heap/store-buffer.cc
diff --git a/src/heap/store-buffer.cc b/src/heap/store-buffer.cc
index 090d996c842993c269582a2d080fc4540a3d2045..1c1676a229fc00d21c0f8634b1bc0d5da99f6ef1 100644
--- a/src/heap/store-buffer.cc
+++ b/src/heap/store-buffer.cc
@@ -578,5 +578,56 @@ void StoreBuffer::Compact() {
   }
   heap_->isolate()->counters()->store_buffer_compactions()->Increment();
 }
+
+
+void StoreBufferRebuilder::Callback(MemoryChunk* page, StoreBufferEvent event) {
+  if (event == kStoreBufferStartScanningPagesEvent) {
+    start_of_current_page_ = NULL;
+    current_page_ = NULL;
+  } else if (event == kStoreBufferScanningPageEvent) {
+    if (current_page_ != NULL) {
+      // If this page already overflowed the store buffer during this iteration.
+      if (current_page_->scan_on_scavenge()) {
+        // Then we should wipe out the entries that have been added for it.
+        store_buffer_->SetTop(start_of_current_page_);
+      } else if (store_buffer_->Top() - start_of_current_page_ >=
+                 (store_buffer_->Limit() - store_buffer_->Top()) >> 2) {
+        // Did we find too many pointers in the previous page?  The heuristic is
+        // that no page can take more then 1/5 the remaining slots in the store
+        // buffer.
+        current_page_->set_scan_on_scavenge(true);
+        store_buffer_->SetTop(start_of_current_page_);
+      } else {
+        // In this case the page we scanned took a reasonable number of slots in
+        // the store buffer.  It has now been rehabilitated and is no longer
+        // marked scan_on_scavenge.
+        DCHECK(!current_page_->scan_on_scavenge());
+      }
+    }
+    start_of_current_page_ = store_buffer_->Top();
+    current_page_ = page;
+  } else if (event == kStoreBufferFullEvent) {
+    // The current page overflowed the store buffer again.  Wipe out its entries
+    // in the store buffer and mark it scan-on-scavenge again.  This may happen
+    // several times while scanning.
+    if (current_page_ == NULL) {
+      // Store Buffer overflowed while scanning promoted objects.  These are not
+      // in any particular page, though they are likely to be clustered by the
+      // allocation routines.
+      store_buffer_->EnsureSpace(StoreBuffer::kStoreBufferSize / 2);
+    } else {
+      // Store Buffer overflowed while scanning a particular old space page for
+      // pointers to new space.
+      DCHECK(current_page_ == page);
+      DCHECK(page != NULL);
+      current_page_->set_scan_on_scavenge(true);
+      DCHECK(start_of_current_page_ != store_buffer_->Top());
+      store_buffer_->SetTop(start_of_current_page_);
+    }
+  } else {
+    UNREACHABLE();
+  }
+}
+
 }  // namespace internal
 }  // namespace v8