Introduce LiteralSet

Source/core/editing/FormatBlockCommand.cpp

Index: Source/core/editing/FormatBlockCommand.cpp
diff --git a/Source/core/editing/FormatBlockCommand.cpp b/Source/core/editing/FormatBlockCommand.cpp
index 6b5337ccaaa3161832bb9d707d8b937825a7c83b..661dac3d9d2cd2493c1312d1a2782caf2433060e 100644
--- a/Source/core/editing/FormatBlockCommand.cpp
+++ b/Source/core/editing/FormatBlockCommand.cpp
@@ -115,34 +115,38 @@ Element* FormatBlockCommand::elementForFormatBlockCommand(Range* range)
     return commonAncestor->isElementNode() ? toElement(commonAncestor) : 0;
 }
 
+// FIXME: This function doesn't work properly for XHTML documents that use a non-standard prefix.
 bool isElementForFormatBlock(const QualifiedName& tagName)
 {
-    DEFINE_STATIC_LOCAL(HashSet<QualifiedName>, blockTags, ());
-    if (blockTags.isEmpty()) {
-        blockTags.add(addressTag);
-        blockTags.add(articleTag);
-        blockTags.add(asideTag);
-        blockTags.add(blockquoteTag);
-        blockTags.add(ddTag);
-        blockTags.add(divTag);
-        blockTags.add(dlTag);
-        blockTags.add(dtTag);
-        blockTags.add(footerTag);
-        blockTags.add(h1Tag);
-        blockTags.add(h2Tag);
-        blockTags.add(h3Tag);
-        blockTags.add(h4Tag);
-        blockTags.add(h5Tag);
-        blockTags.add(h6Tag);
-        blockTags.add(headerTag);
-        blockTags.add(hgroupTag);
-        blockTags.add(mainTag);
-        blockTags.add(navTag);
-        blockTags.add(pTag);
-        blockTags.add(preTag);
-        blockTags.add(sectionTag);
+    DEFINE_STATIC_LOCAL(QualifiedNameLiteralSet, blockTags, ());
+    if (!blockTags.isInitialized()) {
+        static const QualifiedName* blockTagData[] = {
+            &addressTag,
+            &articleTag,
+            &asideTag,
+            &blockquoteTag,
+            &ddTag,
+            &divTag,
+            &dlTag,
+            &dtTag,
+            &footerTag,
+            &h1Tag,
+            &h2Tag,
+            &h3Tag,
+            &h4Tag,
+            &h5Tag,
+            &h6Tag,
+            &headerTag,
+            &hgroupTag,
+            &mainTag,
+            &navTag,
+            &pTag,
+            &preTag,
+            &sectionTag,
+        };
+        blockTags.init(blockTagData, WTF_ARRAY_LENGTH(blockTagData));
     }
-    return blockTags.contains(tagName);
+    return blockTags.contains(&tagName);
 }
 
 Node* enclosingBlockToSplitTreeTo(Node* startNode)