Add unittest for CircularLinkedList + bugfix

dart/runtime/bin/eventhandler.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef BIN_EVENTHANDLER_H_
 #define BIN_EVENTHANDLER_H_
 
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
 #include "bin/isolate_data.h"
@@ skipping 132 matching lines @@
       // Insert e as the last element in the list.
       e->prev_ = head_->prev_;
       e->next_ = head_;
       e->prev_->next_ = e;
       head_->prev_ = e;
       return false;
     }
   }
 
   void RemoveHead() {
+    ASSERT(head_ != NULL);
+
     Entry* e = head_;
     if (e->next_ == e) {
       head_ = NULL;
     } else {
       e->prev_->next_ = e->next_;
       e->next_->prev_ = e->prev_;
       head_ = e->next_;
     }
     delete e;
   }
 
   void Remove(T item) {
     if (head_ == NULL) {
       return;
     } else if (head_ == head_->next_) {
       if (head_->t == item) {
         delete head_;
         head_ = NULL;
         return;
       }
     } else {
       Entry *current = head_;
       do {
         if (current->t == item) {
           Entry *next = current->next_;
           Entry *prev = current->prev_;
           prev->next_ = next;
           next->prev_ = prev;
+
+          if (current == head_) {
+            head_ = head_->next_;
+          }
+
           delete current;
           return;
         }
         current = current->next_;
       } while (current != head_);
     }
   }
 
   void RemoveAll() {
     while (HasHead()) {
       RemoveHead();
     }
   }
 
   T head() const { return head_->t; }
 
   bool HasHead() const {
     return head_ != NULL;
   }
 
   void Rotate() {
     if (head_ != NULL) {
       ASSERT(head_->next_ != NULL);
       head_ = head_->next_;
     }
   }
 
  private:
   struct Entry {
-    explicit Entry(const T& t) : t(t) {}
+    explicit Entry(const T& t) : t(t), next_(NULL), prev_(NULL) {}
     const T t;
     Entry* next_;
     Entry* prev_;
   };
 
   Entry* head_;
 };
 
 
 class DescriptorInfoBase {
@@ skipping 406 matching lines @@
 
  private:
   friend class EventHandlerImplementation;
   EventHandlerImplementation delegate_;
 };
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // BIN_EVENTHANDLER_H_