diff --git a/layout/style/nsCSSRuleProcessor.cpp b/layout/style/nsCSSRuleProcessor.cpp
index c5556a6bfb63..9b7623e814ac 100644
--- a/layout/style/nsCSSRuleProcessor.cpp
+++ b/layout/style/nsCSSRuleProcessor.cpp
@@ -88,7 +88,6 @@
 #include "nsStyleSet.h"
 #include "prlog.h"
 #include "nsIObserverService.h"
-#include "nsIPrivateBrowsingService.h"
 #include "nsNetCID.h"
 #include "mozilla/Services.h"
 #include "mozilla/dom/Element.h"
@@ -1080,63 +1079,6 @@ RuleCascadeData::AttributeListFor(nsIAtom* aAttribute)
   return &entry->mSelectors;
 }
 
-class nsPrivateBrowsingObserver : nsIObserver,
-                                  nsSupportsWeakReference
-{
-public:
-  nsPrivateBrowsingObserver();
-
-  NS_DECL_ISUPPORTS
-  NS_DECL_NSIOBSERVER
-
-  void Init();
-  bool InPrivateBrowsing() const { return mInPrivateBrowsing; }
-
-private:
-  bool mInPrivateBrowsing;
-};
-
-NS_IMPL_ISUPPORTS2(nsPrivateBrowsingObserver, nsIObserver, nsISupportsWeakReference)
-
-nsPrivateBrowsingObserver::nsPrivateBrowsingObserver()
-  : mInPrivateBrowsing(false)
-{
-}
-
-void
-nsPrivateBrowsingObserver::Init()
-{
-  nsCOMPtr<nsIObserverService> observerService =
-    mozilla::services::GetObserverService();
-  if (observerService) {
-    observerService->AddObserver(this, "profile-after-change", true);
-    observerService->AddObserver(this, NS_PRIVATE_BROWSING_SWITCH_TOPIC, true);
-  }
-}
-
-nsresult
-nsPrivateBrowsingObserver::Observe(nsISupports *aSubject,
-                                   const char *aTopic,
-                                   const PRUnichar *aData)
-{
-  if (!strcmp(aTopic, NS_PRIVATE_BROWSING_SWITCH_TOPIC)) {
-    if (!nsCRT::strcmp(aData, NS_LITERAL_STRING(NS_PRIVATE_BROWSING_ENTER).get())) {
-      mInPrivateBrowsing = true;
-    } else {
-      mInPrivateBrowsing = false;
-    }
-  }
-  else if (!strcmp(aTopic, "profile-after-change")) {
-    nsCOMPtr<nsIPrivateBrowsingService> pbService =
-      do_GetService(NS_PRIVATE_BROWSING_SERVICE_CONTRACTID);
-    if (pbService)
-      pbService->GetPrivateBrowsingEnabled(&mInPrivateBrowsing);
-  }
-  return NS_OK;
-}
-
-static nsPrivateBrowsingObserver *gPrivateBrowsingObserver = nsnull;
-
 // -------------------------------
 // CSS Style rule processor implementation
 //
@@ -1170,11 +1112,6 @@ nsCSSRuleProcessor::Startup()
   Preferences::AddBoolVarCache(&gSupportVisitedPseudo, VISITED_PSEUDO_PREF,
                                true);
 
-  gPrivateBrowsingObserver = new nsPrivateBrowsingObserver();
-  NS_ENSURE_TRUE(gPrivateBrowsingObserver, NS_ERROR_OUT_OF_MEMORY);
-  NS_ADDREF(gPrivateBrowsingObserver);
-  gPrivateBrowsingObserver->Init();
-
   return NS_OK;
 }
 
@@ -1311,8 +1248,6 @@ nsCSSRuleProcessor::FreeSystemMetrics()
 nsCSSRuleProcessor::Shutdown()
 {
   FreeSystemMetrics();
-  // Make sure we don't crash if Shutdown is called before Init
-  NS_IF_RELEASE(gPrivateBrowsingObserver);
 }
 
 /* static */ bool
@@ -1336,7 +1271,7 @@ nsCSSRuleProcessor::GetWindowsThemeIdentifier()
 
 /* static */
 nsEventStates
-nsCSSRuleProcessor::GetContentState(Element* aElement)
+nsCSSRuleProcessor::GetContentState(Element* aElement, const TreeMatchContext& aTreeMatchContext)
 {
   nsEventStates state = aElement->StyleState();
 
@@ -1347,7 +1282,7 @@ nsCSSRuleProcessor::GetContentState(Element* aElement)
   if (state.HasState(NS_EVENT_STATE_VISITED) &&
       (!gSupportVisitedPseudo ||
        aElement->OwnerDoc()->IsBeingUsedAsImage() ||
-       gPrivateBrowsingObserver->InPrivateBrowsing())) {
+       aTreeMatchContext.mUsingPrivateBrowsing)) {
     state &= ~NS_EVENT_STATE_VISITED;
     state |= NS_EVENT_STATE_UNVISITED;
   }
@@ -1366,10 +1301,11 @@ nsCSSRuleProcessor::IsLink(Element* aElement)
 nsEventStates
 nsCSSRuleProcessor::GetContentStateForVisitedHandling(
                      Element* aElement,
+                     const TreeMatchContext& aTreeMatchContext,
                      nsRuleWalker::VisitedHandlingType aVisitedHandling,
                      bool aIsRelevantLink)
 {
-  nsEventStates contentState = GetContentState(aElement);
+  nsEventStates contentState = GetContentState(aElement, aTreeMatchContext);
   if (contentState.HasAtLeastOneOfStates(NS_EVENT_STATE_VISITED | NS_EVENT_STATE_UNVISITED)) {
     NS_ABORT_IF_FALSE(IsLink(aElement), "IsLink() should match state");
     contentState &= ~(NS_EVENT_STATE_VISITED | NS_EVENT_STATE_UNVISITED);
@@ -2131,6 +2067,7 @@ static bool SelectorMatches(Element* aElement,
           nsEventStates contentState =
             nsCSSRuleProcessor::GetContentStateForVisitedHandling(
                                          aElement,
+                                         aTreeMatchContext,
                                          aTreeMatchContext.VisitedHandling(),
                                          aNodeMatchContext.mIsRelevantLink);
           if (!contentState.HasAtLeastOneOfStates(statesToCheck)) {
diff --git a/layout/style/nsCSSRuleProcessor.h b/layout/style/nsCSSRuleProcessor.h
index 859adcc0a3ab..205f4932da17 100644
--- a/layout/style/nsCSSRuleProcessor.h
+++ b/layout/style/nsCSSRuleProcessor.h
@@ -103,13 +103,15 @@ public:
    * Helper to get the content state for a content node.  This may be
    * slightly adjusted from IntrinsicState().
    */
-  static nsEventStates GetContentState(mozilla::dom::Element* aElement);
+  static nsEventStates GetContentState(mozilla::dom::Element* aElement,
+                                       const TreeMatchContext& aTreeMatchContext);
 
   /*
    * Helper to get the content state for :visited handling for an element
    */
   static nsEventStates GetContentStateForVisitedHandling(
              mozilla::dom::Element* aElement,
+             const TreeMatchContext& aTreeMatchContext,
              nsRuleWalker::VisitedHandlingType aVisitedHandling,
              bool aIsRelevantLink);
 
diff --git a/layout/style/nsHTMLStyleSheet.cpp b/layout/style/nsHTMLStyleSheet.cpp
index e5dabfaed345..526109dbea1e 100644
--- a/layout/style/nsHTMLStyleSheet.cpp
+++ b/layout/style/nsHTMLStyleSheet.cpp
@@ -212,6 +212,7 @@ nsHTMLStyleSheet::RulesMatching(ElementRuleProcessorData* aData)
       if (mLinkRule || mVisitedRule || mActiveRule) {
         nsEventStates state = nsCSSRuleProcessor::GetContentStateForVisitedHandling(
                                   aData->mElement,
+                                  aData->mTreeMatchContext,
                                   aData->mTreeMatchContext.VisitedHandling(),
                                   // If the node being matched is a link,
                                   // it's the relevant link.
diff --git a/layout/style/nsRuleProcessorData.h b/layout/style/nsRuleProcessorData.h
index 1cf54cc965f8..ecd2ad4eb298 100644
--- a/layout/style/nsRuleProcessorData.h
+++ b/layout/style/nsRuleProcessorData.h
@@ -51,6 +51,7 @@
 #include "nsCSSPseudoElements.h"
 #include "nsRuleWalker.h"
 #include "nsNthIndexCache.h"
+#include "nsILoadContext.h"
 #include "mozilla/BloomFilter.h"
 #include "mozilla/GuardObjects.h"
 
@@ -221,6 +222,9 @@ struct NS_STACK_CLASS TreeMatchContext {
   // An ancestor filter
   AncestorFilter mAncestorFilter;
 
+  // Whether this document is using PB mode
+  bool mUsingPrivateBrowsing;
+
   // Constructor to use when creating a tree match context for styling
   TreeMatchContext(bool aForStyling,
                    nsRuleWalker::VisitedHandlingType aVisitedHandling,
@@ -232,7 +236,16 @@ struct NS_STACK_CLASS TreeMatchContext {
     , mScopedRoot(nsnull)
     , mIsHTMLDocument(aDocument->IsHTML())
     , mCompatMode(aDocument->GetCompatibilityMode())
+    , mUsingPrivateBrowsing(false)
   {
+    nsCOMPtr<nsISupports> container = mDocument->GetContainer();
+    if (container) {
+      nsCOMPtr<nsILoadContext> loadContext = do_QueryInterface(container);
+      NS_ASSERTION(loadContext, "Couldn't get loadContext from container; assuming no private browsing.");
+      if (loadContext) {
+        loadContext->GetUsePrivateBrowsing(&mUsingPrivateBrowsing);
+      }
+    }
   }
 };
 
diff --git a/layout/style/nsStyleSet.cpp b/layout/style/nsStyleSet.cpp
index f6cf047b58a8..073d153a8ff8 100644
--- a/layout/style/nsStyleSet.cpp
+++ b/layout/style/nsStyleSet.cpp
@@ -985,7 +985,7 @@ nsStyleSet::ResolveStyleFor(Element* aElement,
 
   return GetContext(aParentContext, ruleNode, visitedRuleNode,
                     nsCSSRuleProcessor::IsLink(aElement),
-                    nsCSSRuleProcessor::GetContentState(aElement).
+                    nsCSSRuleProcessor::GetContentState(aElement, aTreeMatchContext).
                       HasState(NS_EVENT_STATE_VISITED),
                     nsnull, nsCSSPseudoElements::ePseudo_NotPseudoElement,
                     true, aElement);