Remove the concept of user stylesheets.

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index 15500c05e3f1044605f35c5b8c068109bd7d8ba3..d7b51309516b26f7734161a9793c8392d3d5f921 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -626,8 +626,7 @@ void Document::setCompatibilityMode(CompatibilityMode mode)
     m_compatibilityMode = mode;
     selectorQueryCache().invalidate();
     if (inQuirksMode() != wasInQuirksMode) {
-        // All user stylesheets have to reparse using the different mode.
-        m_styleEngine->clearPageUserSheet();
+        // All injected stylesheets have to reparse using the different mode.
         m_styleEngine->invalidateInjectedStyleSheetCache();
     }
 }