Bug 1212624 - Implement range-based iteration for LinkedList, r=Waldo

mfbt/LinkedList.h

@@ -299,6 +299,26 @@ private:
   LinkedListElement<T> sentinel;
 
 public:
+  class Iterator {
+    T* mCurrent;
+
+  public:
+    explicit Iterator(T* aCurrent) : mCurrent(aCurrent) {}
+
+    T* operator *() const {
+      return mCurrent;
+    }
+
+    const Iterator& operator++() {
+      mCurrent = mCurrent->getNext();
+      return *this;
+    }
+
+    bool operator!=(Iterator& aOther) const {
+      return mCurrent != aOther.mCurrent;
+    }
+  };
+
   LinkedList() : sentinel(LinkedListElement<T>::NODE_KIND_SENTINEL) { }
 
   LinkedList(LinkedList<T>&& aOther)
@@ -383,6 +403,18 @@ public:
     }
   }
 
+  /*
+   * Allow range-based iteration:
+   *
+   *     for (MyElementType* elt : myList) { ... }
+   */
+  Iterator begin() {
+    return Iterator(getFirst());
+  }
+  Iterator end() {
+    return Iterator(nullptr);
+  }
+
   /*
    * Measures the memory consumption of the list excluding |this|.  Note that
    * it only measures the list elements themselves.  If the list elements