- Account for live size in marker.

runtime/vm/pages.cc

Index: runtime/vm/pages.cc
===================================================================
--- runtime/vm/pages.cc	(revision 35390)
+++ runtime/vm/pages.cc	(working copy)
@@ -535,12 +535,12 @@
 
   // Save old value before GCMarker visits the weak persistent handles.
   SpaceUsage usage_before = usage_;
-  usage_.used_in_words = 0;
 
   // Mark all reachable old-gen objects.
   bool collect_code = FLAG_collect_code && ShouldCollectCode();
   GCMarker marker(heap_);
   marker.MarkObjects(isolate, this, invoke_api_callbacks, collect_code);
+  usage_.used_in_words = marker.marked_words();
 
   int64_t mid1 = OS::GetCurrentTimeMicros();
 
@@ -557,12 +557,11 @@
   HeapPage* page = pages_;
   while (page != NULL) {
     HeapPage* next_page = page->next();
-    intptr_t page_in_use = sweeper.SweepPage(page, &freelist_[page->type()]);
-    if (page_in_use == 0) {
+    bool page_in_use = sweeper.SweepPage(page, &freelist_[page->type()]);
+    if (page_in_use) {
+      prev_page = page;
+    } else {
       FreePage(page, prev_page);
-    } else {
-      usage_.used_in_words += (page_in_use >> kWordSizeLog2);
-      prev_page = page;
     }
     // Advance to the next page.
     page = next_page;
@@ -573,13 +572,12 @@
   prev_page = NULL;
   page = large_pages_;
   while (page != NULL) {
-    intptr_t page_in_use = sweeper.SweepLargePage(page);
     HeapPage* next_page = page->next();
-    if (page_in_use == 0) {
+    bool page_in_use = sweeper.SweepLargePage(page);
+    if (page_in_use) {
+      prev_page = page;
+    } else {
       FreeLargePage(page, prev_page);
-    } else {
-      usage_.used_in_words += (page_in_use >> kWordSizeLog2);
-      prev_page = page;
     }
     // Advance to the next page.
     page = next_page;