(Concept patch) Simplify WTF::HashTable::add() return value for size and performance

Source/core/inspector/DOMPatchSupport.cpp

Index: Source/core/inspector/DOMPatchSupport.cpp
diff --git a/Source/core/inspector/DOMPatchSupport.cpp b/Source/core/inspector/DOMPatchSupport.cpp
index a5dc95cd7136982cfe4566cfd082ff96a7f8c83e..813c063dd00aa547ae43b85b87c488aab864f591 100644
--- a/Source/core/inspector/DOMPatchSupport.cpp
+++ b/Source/core/inspector/DOMPatchSupport.cpp
@@ -244,13 +244,11 @@ DOMPatchSupport::diff(const Vector<OwnPtr<Digest> >& oldList, const Vector<OwnPt
     DiffTable oldTable;
 
     for (size_t i = 0; i < newList.size(); ++i) {
-        DiffTable::iterator it = newTable.add(newList[i]->m_sha1, Vector<size_t>()).iterator;
-        it->value.append(i);
+        newTable.add(newList[i]->m_sha1, Vector<size_t>()).iterator->value.append(i);
     }
 
     for (size_t i = 0; i < oldList.size(); ++i) {
-        DiffTable::iterator it = oldTable.add(oldList[i]->m_sha1, Vector<size_t>()).iterator;
-        it->value.append(i);
+        oldTable.add(oldList[i]->m_sha1, Vector<size_t>()).iterator->value.append(i);
     }
 
     for (DiffTable::iterator newIt = newTable.begin(); newIt != newTable.end(); ++newIt) {