Clean up markClientsAndObserversFinished().

Simplify transferring a counted element entry from one set to another.

To do so, add generalized version of add() over HashCountedSet that lets
the caller specify a count.

R=
BUG=

Review-Url: https://codereview.chromium.org/2045883002
Cr-Commit-Position: refs/heads/master@{#398275}

third_party/WebKit/Source/core/fetch/ImageResource.cpp

@@ -106,13 +106,10 @@ void ImageResource::checkNotify()
 
 void ImageResource::markClientsAndObserversFinished()
 {
-    while (!m_observers.isEmpty()) {
-        HashCountedSet<ImageResourceObserver*>::iterator it = m_observers.begin();
-        for (int i = it->value; i; i--) {
-            m_finishedObservers.add(it->key);
-            m_observers.remove(it);
-        }
-    }
+    HashCountedSet<ImageResourceObserver*> observers;
+    m_observers.swap(observers);
+    for (const auto& it : observers)
+        m_finishedObservers.add(it.key, it.value);
 
     Resource::markClientsAndObserversFinished();
 }

third_party/WebKit/Source/core/fetch/Resource.cpp

@@ -394,13 +394,10 @@ void Resource::setDataBufferingPolicy(DataBufferingPolicy dataBufferingPolicy)
 
 void Resource::markClientsAndObserversFinished()
 {
-    while (!m_clients.isEmpty()) {
-        HashCountedSet<ResourceClient*>::iterator it = m_clients.begin();
-        for (int i = it->value; i; i--) {
-            m_finishedClients.add(it->key);
-            m_clients.remove(it);
-        }
-    }
+    HashCountedSet<ResourceClient*> clients;
+    m_clients.swap(clients);
+    for (const auto& it : clients)
+        m_finishedClients.add(it.key, it.value);
 }
 
 void Resource::error(const ResourceError& error)

third_party/WebKit/Source/core/html/HTMLFrameOwnerElement.cpp

@@ -45,7 +45,7 @@ static WidgetToParentMap& widgetNewParentMap()
     return map;
 }
 
-typedef HeapHashSet<Member<Widget>> WidgetSet;
+using WidgetSet = HeapHashSet<Member<Widget>>;
 static WidgetSet& widgetsPendingTemporaryRemovalFromParent()
 {
     // Widgets in this set will not leak because it will be cleared in
@@ -54,9 +54,9 @@ static WidgetSet& widgetsPendingTemporaryRemovalFromParent()
     return set;
 }
 
-HeapHashCountedSet<Member<Node>>& SubframeLoadingDisabler::disabledSubtreeRoots()
+SubframeLoadingDisabler::SubtreeRootSet& SubframeLoadingDisabler::disabledSubtreeRoots()
 {
-    DEFINE_STATIC_LOCAL(HeapHashCountedSet<Member<Node>>, nodes, (new HeapHashCountedSet<Member<Node>>));
+    DEFINE_STATIC_LOCAL(SubtreeRootSet, nodes, (new SubtreeRootSet));
     return nodes;
 }
 

third_party/WebKit/Source/core/html/HTMLFrameOwnerElement.h

@@ -140,7 +140,9 @@ public:
     }
 
 private:
-    CORE_EXPORT static HeapHashCountedSet<Member<Node>>& disabledSubtreeRoots();
+    using SubtreeRootSet = HeapHashCountedSet<Member<Node>>;
+
+    CORE_EXPORT static SubtreeRootSet& disabledSubtreeRoots();
 
     Member<Node> m_root;
 };

third_party/WebKit/Source/wtf/HashCountedSet.h

@@ -71,6 +71,9 @@ public:
     // true if an new entry was added.
     AddResult add(const ValueType&);
 
+    // Generalized add(), adding the value N times.
+    AddResult add(const ValueType&, unsigned);
+
     // Reduces the count of the value, and removes it if count goes down to
     // zero, returns true if the value is removed.
     bool remove(const ValueType& value) { return remove(find(value)); }
@@ -91,13 +94,20 @@ private:
 };
 
 template <typename T, typename U, typename V, typename W>
-inline typename HashCountedSet<T, U, V, W>::AddResult HashCountedSet<T, U, V, W>::add(const ValueType& value)
+inline typename HashCountedSet<T, U, V, W>::AddResult HashCountedSet<T, U, V, W>::add(const ValueType& value, unsigned count)
 {
+    DCHECK_GT(count, 0u);
     AddResult result = m_impl.add(value, 0);
-    ++result.storedValue->value;
+    result.storedValue->value += count;
     return result;
 }
 
+template <typename T, typename U, typename V, typename W>
+inline typename HashCountedSet<T, U, V, W>::AddResult HashCountedSet<T, U, V, W>::add(const ValueType& value)
+{
+    return add(value, 1u);
+}
+
 template <typename T, typename U, typename V, typename W>
 inline bool HashCountedSet<T, U, V, W>::remove(iterator it)
 {