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 e3498d9cfc7c585a7b6a7e372944bf4d04fd32ee..a36d2e733107f418ab7934e697bb16fec6d85881 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();
     }
 }