Added addXSLStyleSheet and removeXSLStyleSheet to StyleEngine.

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 4d1a0b46a5f9118dbc190a660ca1dd11fa76466b..54e73789c503b601860d6dfecaae9327923d471c 100644
--- a/Source/core/dom/StyleEngine.cpp
+++ b/Source/core/dom/StyleEngine.cpp
@@ -75,6 +75,7 @@ StyleEngine::StyleEngine(Document& document)
     // We don't need to create CSSFontSelector for imported document or
     // HTMLTemplateElement's document, because those documents have no frame.
     , m_fontSelector(document.frame() ? CSSFontSelector::create(&document) : nullptr)
+    , m_xslStyleSheet(nullptr)
 {
 }
 
@@ -285,7 +286,7 @@ void StyleEngine::addStyleSheetCandidateNode(Node* node, bool createdByParser)
 
     TreeScope& treeScope = isHTMLStyleElement(*node) ? node->treeScope() : *m_document;
     ASSERT(isHTMLStyleElement(node) || treeScope == m_document);
-
+    ASSERT(!isXSLStyleSheet(node));
     TreeScopeStyleSheetCollection* collection = ensureStyleSheetCollectionFor(treeScope);
     ASSERT(collection);
     collection->addStyleSheetCandidateNode(node, createdByParser);
@@ -303,6 +304,7 @@ void StyleEngine::removeStyleSheetCandidateNode(Node* node)
 void StyleEngine::removeStyleSheetCandidateNode(Node* node, ContainerNode* scopingNode, TreeScope& treeScope)
 {
     ASSERT(isHTMLStyleElement(node) || treeScope == m_document);
+    ASSERT(!isXSLStyleSheet(node));
 
     TreeScopeStyleSheetCollection* collection = styleSheetCollectionFor(treeScope);
     ASSERT(collection);
@@ -312,6 +314,37 @@ void StyleEngine::removeStyleSheetCandidateNode(Node* node, ContainerNode* scopi
     m_activeTreeScopes.remove(&treeScope);
 }
 
+void StyleEngine::addXSLStyleSheet(ProcessingInstruction* node, bool createdByParser)
+{
+    if (!node->inDocument())
+        return;
+
+    ASSERT(isXSLStyleSheet(node));
+    bool needToUpdate = false;
+    if (createdByParser || !m_xslStyleSheet) {
+        needToUpdate = !m_xslStyleSheet;
+    } else {
+        unsigned position = m_xslStyleSheet->compareDocumentPositionInternal(node, Node::TreatShadowTreesAsDisconnected);
+        needToUpdate = position & Node::DOCUMENT_POSITION_FOLLOWING;
+    }
+
+    if (!needToUpdate)
+        return;
+
+    markTreeScopeDirty(*m_document);
+    m_xslStyleSheet = node;
+}
+
+void StyleEngine::removeXSLStyleSheet(ProcessingInstruction* node)
+{
+    ASSERT(isXSLStyleSheet(node));
+    if (m_xslStyleSheet != node)
+        return;
+
+    markTreeScopeDirty(*m_document);
+    m_xslStyleSheet = nullptr;
+}
+
 void StyleEngine::modifiedStyleSheetCandidateNode(Node* node)
 {
     if (!node->inDocument())
@@ -493,6 +526,13 @@ bool StyleEngine::shouldClearResolver() const
     return !m_didCalculateResolver && !haveStylesheetsLoaded();
 }
 
+bool StyleEngine::shouldApplyXSLTransform() const
+{
+    if (!RuntimeEnabledFeatures::xsltEnabled())
+        return false;
+    return m_xslStyleSheet && !m_document->transformSourceDocument();
+}
+
 StyleResolverChange StyleEngine::resolverChanged(StyleResolverUpdateMode mode)
 {
     StyleResolverChange change;
@@ -510,6 +550,15 @@ StyleResolverChange StyleEngine::resolverChanged(StyleResolverUpdateMode mode)
         return change;
     }
 
+    if (shouldApplyXSLTransform()) {
+        // Processing instruction (XML documents only).
+        // We don't support linking to embedded CSS stylesheets, see <https://bugs.webkit.org/show_bug.cgi?id=49281> for discussion.
+        // Don't apply XSL transforms to already transformed documents -- <rdar://problem/4132806>
+        if (!m_document->parsing() && !m_xslStyleSheet->isLoading())
+            m_document->applyXSLTransform(m_xslStyleSheet.get());
+        return change;
+    }
+
     m_didCalculateResolver = true;
     if (document().didLayoutWithPendingStylesheets() && !hasPendingSheets())
         change.setNeedsRepaint();