Implement a 2-pass heap verification algorithm.

runtime/vm/heap.h

Index: runtime/vm/heap.h
diff --git a/runtime/vm/heap.h b/runtime/vm/heap.h
index 4e59ff0f64591ab0118a626afb99c7bfed666e99..392e6f375779051abe899c13b8ed7ad7f291399f 100644
--- a/runtime/vm/heap.h
+++ b/runtime/vm/heap.h
@@ -17,6 +17,7 @@ namespace dart {
 // Forward declarations.
 class Isolate;
 class ObjectPointerVisitor;
+class ObjectSet;
 class VirtualMemory;
 
 DECLARE_FLAG(bool, verbose_gc);
@@ -80,11 +81,17 @@ class Heap {
   bool CodeContains(uword addr) const;
   bool StubCodeContains(uword addr) const;
 
+  // Visit all pointers.
+  void IteratePointers(ObjectPointerVisitor* visitor);
+
   // Visit all pointers in the space.
   void IterateNewPointers(ObjectPointerVisitor* visitor);
   void IterateOldPointers(ObjectPointerVisitor* visitor);
   void IterateCodePointers(ObjectPointerVisitor* visitor);
 
+  // Visit all objects.
+  void IterateObjects(ObjectVisitor* visitor);
+
   // Visit all object in the space.
   void IterateNewObjects(ObjectVisitor* visitor);
   void IterateOldObjects(ObjectVisitor* visitor);
@@ -122,6 +129,11 @@ class Heap {
   // Print heap sizes.
   void PrintSizes() const;
 
+  // Returns the [lowest, highest) addresses in the heap.
+  void StartEndAddress(uword* start, uword* end) const;
+
+  ObjectSet* CreateAllocatedObjectSet() const;
+
   // Generates a profile of the current and VM isolate heaps.
   void Profile(Dart_HeapProfileWriteCallback callback, void* stream) const;