applyXSLTransform is too eager

Source/core/dom/StyleSheetCollection.cpp

Index: Source/core/dom/StyleSheetCollection.cpp
diff --git a/Source/core/dom/StyleSheetCollection.cpp b/Source/core/dom/StyleSheetCollection.cpp
index 52fbaed865e45042e4a6af0721859fe9a6215bac..80ca3d2a96764e872e2b7d9936a23de390a8d203 100644
--- a/Source/core/dom/StyleSheetCollection.cpp
+++ b/Source/core/dom/StyleSheetCollection.cpp
@@ -97,14 +97,14 @@ void StyleSheetCollection::collectStyleSheets(DocumentStyleSheetCollection* coll
         Node* n = *it;
         StyleSheet* sheet = 0;
         CSSStyleSheet* activeSheet = 0;
-        if (n->nodeType() == Node::PROCESSING_INSTRUCTION_NODE) {
+        if (n->nodeType() == Node::PROCESSING_INSTRUCTION_NODE && !document()->isHTMLDocument()) {
             // 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.
             ProcessingInstruction* pi = static_cast<ProcessingInstruction*>(n);
             // Don't apply XSL transforms to already transformed documents -- <rdar://problem/4132806>
             if (pi->isXSL() && !document()->transformSourceDocument()) {
                 // Don't apply XSL transforms until loading is finished.
-                if (!document()->parsing())
+                if (!document()->parsing() && !pi->isLoading())
                     document()->applyXSLTransform(pi);
                 return;
             }