- Revert r24564 and r24563 due to unexplained malloc corruption.

runtime/vm/gc_marker.cc

Index: runtime/vm/gc_marker.cc
===================================================================
--- runtime/vm/gc_marker.cc	(revision 24564)
+++ runtime/vm/gc_marker.cc	(working copy)
@@ -379,21 +379,18 @@
 }
 
 
-void GCMarker::ProcessWeakTables(PageSpace* page_space) {
-  for (int sel = 0;
-       sel < Heap::kNumWeakSelectors;
-       sel++) {
-    WeakTable* table = heap_->GetWeakTable(
-        Heap::kOld, static_cast<Heap::WeakSelector>(sel));
-    intptr_t size = table->size();
-    for (intptr_t i = 0; i < size; i++) {
-      if (table->IsValidEntryAt(i)) {
-        RawObject* raw_obj = table->ObjectAt(i);
-        ASSERT(raw_obj->IsHeapObject());
-        if (!raw_obj->IsMarked()) {
-          table->InvalidateAt(i);
-        }
-      }
+void GCMarker::ProcessPeerReferents(PageSpace* page_space) {
+  PageSpace::PeerTable* peer_table = page_space->GetPeerTable();
+  PageSpace::PeerTable::iterator it = peer_table->begin();
+  while (it != peer_table->end()) {
+    RawObject* raw_obj = it->first;
+    ASSERT(raw_obj->IsHeapObject());
+    if (raw_obj->IsMarked()) {
+      // The object has survived.  Do nothing.
+      ++it;
+    } else {
+      // The object has become garbage.  Remove its record.
+      peer_table->erase(it++);
     }
   }
 }
@@ -411,7 +408,7 @@
   MarkingWeakVisitor mark_weak;
   IterateWeakRoots(isolate, &mark_weak, invoke_api_callbacks);
   mark.Finalize();
-  ProcessWeakTables(page_space);
+  ProcessPeerReferents(page_space);
   Epilogue(isolate, invoke_api_callbacks);
 }