Added {Zone}GrowableHandlePtrArray types: simplifies code, makes code safer

runtime/vm/growable_array.h

Index: runtime/vm/growable_array.h
diff --git a/runtime/vm/growable_array.h b/runtime/vm/growable_array.h
index 1e7c2041f8a86d94429ec8260821fd51ea3c1d11..88163fbb1f5ab5b1a424be5d63f3fc996d419250 100644
--- a/runtime/vm/growable_array.h
+++ b/runtime/vm/growable_array.h
@@ -195,6 +195,57 @@ class ZoneGrowableArray : public BaseGrowableArray<T, ZoneAllocated> {
 };
 
 
+// T must be a Handle type.
+template<typename T, typename B>
+class BaseGrowableHandlePtrArray : public B {
+ public:
+  BaseGrowableHandlePtrArray(Zone* zone, intptr_t initial_capacity)
+      : zone_(zone), array_(zone, initial_capacity) {}
+
+  // Use unique zone handles to store objects.
+  void Add(const T& t) {
+    array_.Add(&T::ZoneHandle(zone_, t.raw()));
+  }
+
+  T& operator[](intptr_t index) const {
+    return *array_[index];
+  }
+
+  const T& At(intptr_t index) const {
+    return operator[](index);
+  }
+
+  intptr_t length() const { return array_.length(); }
+
+  const GrowableArray<T*>& growable_array() const { return array_; }
+
+ private:
+  Zone* zone_;
+  GrowableArray<T*> array_;
+
+  DISALLOW_COPY_AND_ASSIGN(BaseGrowableHandlePtrArray);
+};
+
+
+template<typename T>
+class GrowableHandlePtrArray :
+    public BaseGrowableHandlePtrArray<T, ValueObject> {
+ public:
+  GrowableHandlePtrArray(Zone* zone, intptr_t initial_capacity)
+      : BaseGrowableHandlePtrArray<T, ValueObject>(zone, initial_capacity) {}
+};
+
+
+template<typename T>
+class ZoneGrowableHandlePtrArray :
+    public BaseGrowableHandlePtrArray<T, ZoneAllocated> {
+ public:
+  ZoneGrowableHandlePtrArray(Zone* zone, intptr_t initial_capacity)
+      : BaseGrowableHandlePtrArray<T, ZoneAllocated>(zone, initial_capacity) {}
+};
+
+
+
 class Malloc : public AllStatic {
  public:
   template <class T>