Use an AtomicString as key in DocumentOrderedMap

Use an AtomicString as key in DocumentOrderedMap instead of a StringImpl*.
This is safer as the HashMap Traits rely on the StringImpl* to not be a
dangling pointer (it is calling StringImpl::hash()). Using an AtomicString
as key will make sure we don't experience use-after-free such as in Bug
402255.

I ran Bindings/get-element-by-id.html test and did not see any performance
regression.

R=esprehn@chromium.org, morrita@chromium.org
BUG=402255

Review URL: https://codereview.chromium.org/467973003

git-svn-id: svn://svn.chromium.org/blink/trunk@180365 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/dom/DocumentOrderedMap.cpp

@@ -71,7 +71,7 @@ void DocumentOrderedMap::add(const AtomicString& key, Element* element)
     ASSERT(key);
     ASSERT(element);
 
-    Map::AddResult addResult = m_map.add(key.impl(), adoptPtrWillBeNoop(new MapEntry(element)));
+    Map::AddResult addResult = m_map.add(key, adoptPtrWillBeNoop(new MapEntry(element)));
     if (addResult.isNewEntry)
         return;
 
@@ -87,7 +87,7 @@ void DocumentOrderedMap::remove(const AtomicString& key, Element* element)
     ASSERT(key);
     ASSERT(element);
 
-    Map::iterator it = m_map.find(key.impl());
+    Map::iterator it = m_map.find(key);
     if (it == m_map.end())
         return;
 
@@ -112,7 +112,7 @@ inline Element* DocumentOrderedMap::get(const AtomicString& key, const TreeScope
     ASSERT(key);
     ASSERT(scope);
 
-    MapEntry* entry = m_map.get(key.impl());
+    MapEntry* entry = m_map.get(key);
     if (!entry)
         return 0;
 
@@ -142,7 +142,7 @@ const WillBeHeapVector<RawPtrWillBeMember<Element> >& DocumentOrderedMap::getAll
     ASSERT(scope);
     DEFINE_STATIC_LOCAL(OwnPtrWillBePersistent<WillBeHeapVector<RawPtrWillBeMember<Element> > >, emptyVector, (adoptPtrWillBeNoop(new WillBeHeapVector<RawPtrWillBeMember<Element> >())));
 
-    Map::iterator it = m_map.find(key.impl());
+    Map::iterator it = m_map.find(key);
     if (it == m_map.end())
         return *emptyVector;
 

third_party/WebKit/Source/core/dom/DocumentOrderedMap.h

@@ -35,6 +35,7 @@
 #include "wtf/Forward.h"
 #include "wtf/HashMap.h"
 #include "wtf/text/AtomicString.h"
+#include "wtf/text/AtomicStringHash.h"
 #include "wtf/text/StringImpl.h"
 
 namespace blink {
@@ -78,19 +79,19 @@ private:
         WillBeHeapVector<RawPtrWillBeMember<Element> > orderedList;
     };
 
-    typedef WillBeHeapHashMap<StringImpl*, OwnPtrWillBeMember<MapEntry> > Map;
+    typedef WillBeHeapHashMap<AtomicString, OwnPtrWillBeMember<MapEntry> > Map;
 
     mutable Map m_map;
 };
 
 inline bool DocumentOrderedMap::contains(const AtomicString& id) const
 {
-    return m_map.contains(id.impl());
+    return m_map.contains(id);
 }
 
 inline bool DocumentOrderedMap::containsMultiple(const AtomicString& id) const
 {
-    Map::const_iterator it = m_map.find(id.impl());
+    Map::const_iterator it = m_map.find(id);
     return it != m_map.end() && it->value->count > 1;
 }