Fix ListHashSet::AddResult storing a Node* instead of a ValueType*.

ListHashSet::add() and similar used to return an AddResult value
containing a pointer to ListHashSetNode, instead of an actual value
specified by the user. This is unintuitive, and the users are forced to
append "->m_value" to obtain a pointer to the object they've really
added.

This patch fixes this issue, and giving what the users usually expect.

Interestingly, no production code (outside of tests) made use of
storedValue. LinkedHashSet did not have this issue.

BUG=582349

Review URL: https://codereview.chromium.org/1813693002

Cr-Commit-Position: refs/heads/master@{#381680}

third_party/WebKit/Source/wtf/ListHashSet.h

@@ -87,13 +87,18 @@ public:
     friend class ListHashSetReverseIterator<ListHashSet>;
     friend class ListHashSetConstReverseIterator<ListHashSet>;
 
-    template <typename ValueType> struct HashTableAddResult final {
+    struct AddResult final {
         STACK_ALLOCATED();
-        HashTableAddResult(Node* storedValue, bool isNewEntry) : storedValue(storedValue), isNewEntry(isNewEntry) { }
-        Node* storedValue;
+        friend class ListHashSet<ValueArg, inlineCapacity, HashArg, AllocatorArg>;
+        AddResult(Node* node, bool isNewEntry)
+            : storedValue(&node->m_value)
+            , isNewEntry(isNewEntry)
+            , m_node(node) { }
+        ValueType* storedValue;
         bool isNewEntry;
+    private:
+        Node* m_node;
     };
-    typedef HashTableAddResult<ValueType> AddResult;
 
     ListHashSet();
     ListHashSet(const ListHashSet&);
@@ -841,7 +846,7 @@ typename ListHashSet<T, inlineCapacity, U, V>::AddResult ListHashSet<T, inlineCa
 template <typename T, size_t inlineCapacity, typename U, typename V>
 typename ListHashSet<T, inlineCapacity, U, V>::iterator ListHashSet<T, inlineCapacity, U, V>::addReturnIterator(ValuePassInType value)
 {
-    return makeIterator(add(value).storedValue);
+    return makeIterator(add(value).m_node);
 }
 
 template <typename T, size_t inlineCapacity, typename U, typename V>

third_party/WebKit/Source/wtf/ListHashSetTest.cpp

@@ -560,7 +560,7 @@ TEST(ListHashSetTest, WithOwnPtr)
         // AddResult in a separate scope to avoid assertion hit,
         // since we modify the container further.
         OwnPtrSet::AddResult res1 = set.add(adoptPtr(ptr1));
-        EXPECT_EQ(res1.storedValue->m_value.get(), ptr1);
+        EXPECT_EQ(res1.storedValue->get(), ptr1);
     }
 
     EXPECT_FALSE(deleted1);
@@ -572,7 +572,7 @@ TEST(ListHashSetTest, WithOwnPtr)
     Dummy* ptr2 = new Dummy(deleted2);
     {
         OwnPtrSet::AddResult res2 = set.add(adoptPtr(ptr2));
-        EXPECT_EQ(res2.storedValue->m_value.get(), ptr2);
+        EXPECT_EQ(res2.storedValue->get(), ptr2);
     }
 
     EXPECT_FALSE(deleted2);