Fixes memory leak of async directory lister

runtime/bin/directory.h

Index: runtime/bin/directory.h
diff --git a/runtime/bin/directory.h b/runtime/bin/directory.h
index 7a1c5d13914e0f8f5daba773f975cb2c49f8d67f..09f479bf21e60ac9aa393e4dc0cec01e67828aa1 100644
--- a/runtime/bin/directory.h
+++ b/runtime/bin/directory.h
@@ -7,6 +7,7 @@
 
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
+#include "bin/reference_counting.h"
 #include "bin/thread.h"
 #include "platform/globals.h"
 
@@ -107,9 +108,7 @@ class DirectoryListing {
   }
 
   virtual ~DirectoryListing() {
-    while (!IsEmpty()) {
-      Pop();
-    }
+    PopAll();
   }
 
   virtual bool HandleDirectory(const char* dir_name) = 0;
@@ -133,6 +132,12 @@ class DirectoryListing {
     return top_ == NULL;
   }
 
+  void PopAll() {
+    while (!IsEmpty()) {
+      Pop();
+    }
+  }
+
   DirectoryListingEntry* top() const {
     return top_;
   }
@@ -166,7 +171,8 @@ class DirectoryListing {
 };
 
 
-class AsyncDirectoryListing : public DirectoryListing {
+class AsyncDirectoryListing : public ReferenceCounted<AsyncDirectoryListing>,
+                              public DirectoryListing {
  public:
   enum Response {
     kListFile = 0,
@@ -179,9 +185,13 @@ class AsyncDirectoryListing : public DirectoryListing {
   AsyncDirectoryListing(const char* dir_name,
                         bool recursive,
                         bool follow_links)
-      : DirectoryListing(dir_name, recursive, follow_links) {}
+      : ReferenceCounted(),
+        DirectoryListing(dir_name, recursive, follow_links),
+        array_(NULL),
+        index_(0),
+        length_(0),
+        weak_handle_(NULL) {}
 
-  virtual ~AsyncDirectoryListing() {}
   virtual bool HandleDirectory(const char* dir_name);
   virtual bool HandleFile(const char* file_name);
   virtual bool HandleLink(const char* file_name);
@@ -199,12 +209,32 @@ class AsyncDirectoryListing : public DirectoryListing {
     return index_;
   }
 
+  // Returns the weak persistent handle for the Dart wrapper.
+  Dart_WeakPersistentHandle WeakHandle() const { return weak_handle_; }
+
+  // Set the weak persistent handle for the Dart wrapper.
+  void SetWeakHandle(Dart_WeakPersistentHandle handle) {
+    ASSERT(weak_handle_ == NULL);
+    weak_handle_ = handle;
+  }
+
+  // Deletes the weak persistent handle for the Dart wrapper. Call
+  // when the listing is explicitly closed and the finalizer is no longer
+  // needed.
+  void DeleteWeakHandle(Dart_Isolate isolate) {
+    Dart_DeleteWeakPersistentHandle(isolate, weak_handle_);
+    weak_handle_ = NULL;
+  }
+
  private:
+  virtual ~AsyncDirectoryListing() {}
   bool AddFileSystemEntityToResponse(Response response, const char* arg);
   CObjectArray* array_;
   intptr_t index_;
   intptr_t length_;
+  Dart_WeakPersistentHandle weak_handle_;
 
+  friend class ReferenceCounted<AsyncDirectoryListing>;
   DISALLOW_IMPLICIT_CONSTRUCTORS(AsyncDirectoryListing);
 };
 
@@ -238,6 +268,7 @@ class SyncDirectoryListing: public DirectoryListing {
   Dart_Handle file_type_;
   Dart_Handle link_type_;
 
+  DISALLOW_ALLOCATION()
   DISALLOW_IMPLICIT_CONSTRUCTORS(SyncDirectoryListing);
 };