Add removeAll method to sets and maps and use them

Source/core/dom/StyleEngine.cpp

Index: Source/core/dom/StyleEngine.cpp
diff --git a/Source/core/dom/StyleEngine.cpp b/Source/core/dom/StyleEngine.cpp
index 970c5714577eb90e617a9e77c0156f7259f834aa..b07470f7f17698fccd7f5a618ef2a3b493c16b7c 100644
--- a/Source/core/dom/StyleEngine.cpp
+++ b/Source/core/dom/StyleEngine.cpp
@@ -380,9 +380,7 @@ bool StyleEngine::updateActiveStyleSheets(StyleResolverUpdateMode updateMode)
             if (!collection->hasStyleSheetCandidateNodes())
                 treeScopesRemoved.add(treeScope);
         }
-        if (!treeScopesRemoved.isEmpty())
-            for (HashSet<TreeScope*>::iterator it = treeScopesRemoved.begin(); it != treeScopesRemoved.end(); ++it)
-                m_activeTreeScopes.remove(*it);
+        m_activeTreeScopes.removeAll(treeScopesRemoved);
     }
 
     InspectorInstrumentation::activeStyleSheetsUpdated(&m_document);