diff --git a/mozilla/content/base/public/nsIStyleRuleSupplier.h b/mozilla/content/base/public/nsIStyleRuleSupplier.h
index 08278facaa9..45da063535a 100644
--- a/mozilla/content/base/public/nsIStyleRuleSupplier.h
+++ b/mozilla/content/base/public/nsIStyleRuleSupplier.h
@@ -20,6 +20,9 @@ class nsIStyleRuleSupplier : public nsISupports {
                        nsISupportsArrayEnumFunc aFunc, void* aData,
                        nsIContent* aContent)=0;
   NS_IMETHOD MatchesScopedRoot(nsIContent* aContent, PRBool* aResult)=0;
+
+  NS_IMETHOD AttributeAffectsStyle(nsISupportsArrayEnumFunc aFunc, void* aData, nsIContent* aContent,
+                                   PRBool* aAffects)=0;
 };
 
 #endif /* _nsIStyleRuleSupplier_h */
diff --git a/mozilla/content/base/src/nsStyleSet.cpp b/mozilla/content/base/src/nsStyleSet.cpp
index 8628adb3df8..9f30dfb1fd6 100644
--- a/mozilla/content/base/src/nsStyleSet.cpp
+++ b/mozilla/content/base/src/nsStyleSet.cpp
@@ -1937,15 +1937,22 @@ StyleSetImpl::AttributeAffectsStyle(nsIAtom *aAttribute, nsIContent *aContent,
   pair.attribute = aAttribute;
   pair.content = aContent;
 
-  /* check until we find a sheet that will be affected */
-  if ((mDocSheets && !mDocSheets->EnumerateForwards(EnumAffectsStyle, &pair)) ||
-      (mOverrideSheets && !mOverrideSheets->EnumerateForwards(EnumAffectsStyle,
-                                                              &pair)) ||
-      (mBackstopSheets && !mBackstopSheets->EnumerateForwards(EnumAffectsStyle,
-                                                              &pair))) {
-    aAffects = PR_TRUE;
-  } else {
-    aAffects = PR_FALSE;
+  /* scoped sheets should be checked first, since - if present - they will contain
+     the bulk of the applicable rules for the content node. */
+  if (mStyleRuleSupplier)
+    mStyleRuleSupplier->AttributeAffectsStyle(EnumAffectsStyle, &pair, aContent, &aAffects);
+
+  if (!aAffects) {
+    /* check until we find a sheet that will be affected */
+    if ((mDocSheets && !mDocSheets->EnumerateForwards(EnumAffectsStyle, &pair)) ||
+        (mOverrideSheets && !mOverrideSheets->EnumerateForwards(EnumAffectsStyle,
+                                                                &pair)) ||
+        (mBackstopSheets && !mBackstopSheets->EnumerateForwards(EnumAffectsStyle,
+                                                                &pair))) {
+      aAffects = PR_TRUE;
+    } else {
+      aAffects = PR_FALSE;
+    }
   }
 
   return NS_OK;
diff --git a/mozilla/content/xbl/public/nsIXBLBinding.h b/mozilla/content/xbl/public/nsIXBLBinding.h
index a0e48d5ddb5..bd1c00a5590 100644
--- a/mozilla/content/xbl/public/nsIXBLBinding.h
+++ b/mozilla/content/xbl/public/nsIXBLBinding.h
@@ -102,6 +102,7 @@ public:
 
   NS_IMETHOD InheritsStyle(PRBool* aResult)=0;
   NS_IMETHOD WalkRules(nsISupportsArrayEnumFunc aFunc, void* aData)=0;
+  NS_IMETHOD AttributeAffectsStyle(nsISupportsArrayEnumFunc aFunc, void* aData, PRBool* aAffects)=0;
 
   NS_IMETHOD MarkForDeath()=0;
   NS_IMETHOD MarkedForDeath(PRBool* aResult)=0;
diff --git a/mozilla/content/xbl/public/nsIXBLPrototypeBinding.h b/mozilla/content/xbl/public/nsIXBLPrototypeBinding.h
index c3216905ef9..40355d55ad8 100644
--- a/mozilla/content/xbl/public/nsIXBLPrototypeBinding.h
+++ b/mozilla/content/xbl/public/nsIXBLPrototypeBinding.h
@@ -77,6 +77,7 @@ public:
   NS_IMETHOD SetInitialAttributes(nsIContent* aBoundElement, nsIContent* aAnonymousContent)=0;
 
   NS_IMETHOD GetRuleProcessors(nsISupportsArray** aResult)=0;
+  NS_IMETHOD GetStyleSheets(nsISupportsArray** aResult)=0;
 
   NS_IMETHOD HasInsertionPoints(PRBool* aResult)=0;
   NS_IMETHOD HasStyleSheets(PRBool* aResult)=0; 
diff --git a/mozilla/content/xbl/src/nsBindingManager.cpp b/mozilla/content/xbl/src/nsBindingManager.cpp
index 6e4601d9da7..f558f5105ce 100644
--- a/mozilla/content/xbl/src/nsBindingManager.cpp
+++ b/mozilla/content/xbl/src/nsBindingManager.cpp
@@ -348,6 +348,7 @@ public:
                        nsISupportsArrayEnumFunc aFunc, void* aData,
                        nsIContent* aContent);
   NS_IMETHOD MatchesScopedRoot(nsIContent* aContent, PRBool* aResult);
+  NS_IMETHOD AttributeAffectsStyle(nsISupportsArrayEnumFunc aFunc, void* aData, nsIContent* aContent, PRBool* aAffects);
 
   // nsIDocumentObserver
   NS_IMETHOD BeginUpdate(nsIDocument* aDocument) { return NS_OK; }
@@ -411,6 +412,9 @@ protected:
   void WalkRules(nsISupportsArrayEnumFunc aFunc, void* aData,
                  nsIContent* aParent, nsIContent* aCurrContent);
 
+  void AttributeAffectsStyle(nsISupportsArrayEnumFunc aFunc, void* aData,
+                             nsIContent* aParent, nsIContent* aCurrContent, PRBool* aAffects);
+
   nsresult GetNestedInsertionPoint(nsIContent* aParent, nsIContent* aChild, nsIContent** aResult);
 
 // MEMBER VARIABLES
@@ -1246,6 +1250,47 @@ nsBindingManager::WalkRules(nsIStyleSet* aStyleSet,
   return NS_OK;
 }
 
+void
+nsBindingManager::AttributeAffectsStyle(nsISupportsArrayEnumFunc aFunc, void* aData,
+                                        nsIContent* aParent, nsIContent* aCurrContent, PRBool* aAffects)
+{    
+  nsCOMPtr<nsIXBLBinding> binding;
+  GetBinding(aCurrContent, getter_AddRefs(binding));
+  if (binding) {
+    binding->AttributeAffectsStyle(aFunc, aData, aAffects);
+  }
+
+  if (*aAffects)
+    return;
+
+  if (aParent != aCurrContent) {
+    nsCOMPtr<nsIContent> par;
+    GetEnclosingScope(aCurrContent, getter_AddRefs(par));
+    if (par)
+      AttributeAffectsStyle(aFunc, aData, aParent, par, aAffects);
+  }
+}
+
+
+NS_IMETHODIMP
+nsBindingManager::AttributeAffectsStyle(nsISupportsArrayEnumFunc aFunc, void* aData, 
+                                        nsIContent* aContent, PRBool* aAffects)
+{
+  *aAffects = PR_FALSE;
+  if (!aContent)
+    return NS_OK;
+
+  nsCOMPtr<nsIContent> parent;
+  GetOutermostStyleScope(aContent, getter_AddRefs(parent));
+
+  AttributeAffectsStyle(aFunc, aData, parent, aContent, aAffects);
+
+  if (*aAffects)
+    return NS_OK;
+
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 nsBindingManager::ShouldBuildChildFrames(nsIContent* aContent, PRBool* aResult)
 {
diff --git a/mozilla/content/xbl/src/nsXBLBinding.cpp b/mozilla/content/xbl/src/nsXBLBinding.cpp
index 4895078d460..4b2ae7f43b2 100644
--- a/mozilla/content/xbl/src/nsXBLBinding.cpp
+++ b/mozilla/content/xbl/src/nsXBLBinding.cpp
@@ -1490,6 +1490,31 @@ nsXBLBinding::WalkRules(nsISupportsArrayEnumFunc aFunc, void* aData)
   return rv;
 }
 
+NS_IMETHODIMP
+nsXBLBinding::AttributeAffectsStyle(nsISupportsArrayEnumFunc aFunc, void* aData, PRBool* aAffects)
+{
+  nsresult rv = NS_OK;
+  if (mNextBinding) {
+    rv = mNextBinding->AttributeAffectsStyle(aFunc, aData, aAffects);
+    if (NS_FAILED(rv))
+      return rv;
+
+    if (*aAffects)
+      return NS_OK;
+  }
+
+  nsCOMPtr<nsISupportsArray> sheets;
+  mPrototypeBinding->GetStyleSheets(getter_AddRefs(sheets));
+  if (sheets) {
+    if (!sheets->EnumerateForwards(aFunc, aData))
+      *aAffects = PR_TRUE;
+    else
+      *aAffects = PR_FALSE;
+  }
+  
+  return rv;
+}
+
 // Internal helper methods ////////////////////////////////////////////////////////////////
 
 NS_IMETHODIMP
diff --git a/mozilla/content/xbl/src/nsXBLBinding.h b/mozilla/content/xbl/src/nsXBLBinding.h
index a24d0e9edee..ac59235609c 100644
--- a/mozilla/content/xbl/src/nsXBLBinding.h
+++ b/mozilla/content/xbl/src/nsXBLBinding.h
@@ -95,6 +95,7 @@ class nsXBLBinding: public nsIXBLBinding
 
   NS_IMETHOD InheritsStyle(PRBool* aResult);
   NS_IMETHOD WalkRules(nsISupportsArrayEnumFunc aFunc, void* aData);
+  NS_IMETHOD AttributeAffectsStyle(nsISupportsArrayEnumFunc aFunc, void* aData, PRBool* aAffects);
 
   NS_IMETHOD MarkForDeath();
   NS_IMETHOD MarkedForDeath(PRBool* aResult);
diff --git a/mozilla/content/xbl/src/nsXBLPrototypeBinding.cpp b/mozilla/content/xbl/src/nsXBLPrototypeBinding.cpp
index e5e85dc5ad6..ecc291ab5dd 100644
--- a/mozilla/content/xbl/src/nsXBLPrototypeBinding.cpp
+++ b/mozilla/content/xbl/src/nsXBLPrototypeBinding.cpp
@@ -1043,6 +1043,14 @@ nsXBLPrototypeBinding::GetRuleProcessors(nsISupportsArray** aResult)
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsXBLPrototypeBinding::GetStyleSheets(nsISupportsArray** aResult)
+{
+  *aResult = mStyleSheetList;
+  NS_IF_ADDREF(*aResult);
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 nsXBLPrototypeBinding::ShouldBuildChildFrames(PRBool* aResult)
 {
diff --git a/mozilla/content/xbl/src/nsXBLPrototypeBinding.h b/mozilla/content/xbl/src/nsXBLPrototypeBinding.h
index c832dea8f86..4bf4e9b0ad5 100644
--- a/mozilla/content/xbl/src/nsXBLPrototypeBinding.h
+++ b/mozilla/content/xbl/src/nsXBLPrototypeBinding.h
@@ -81,6 +81,7 @@ class nsXBLPrototypeBinding: public nsIXBLPrototypeBinding, public nsICSSLoaderO
   NS_IMETHOD SetInitialAttributes(nsIContent* aBoundElement, nsIContent* aAnonymousContent);
 
   NS_IMETHOD GetRuleProcessors(nsISupportsArray** aResult);
+  NS_IMETHOD GetStyleSheets(nsISupportsArray** aResult);
 
   NS_IMETHOD HasInsertionPoints(PRBool* aResult) { *aResult = (mInsertionPointTable != nsnull); return NS_OK; };
   NS_IMETHOD HasStyleSheets(PRBool* aResult) { *aResult = (mStyleSheetList != nsnull); return NS_OK; };
diff --git a/mozilla/layout/style/nsIStyleRuleSupplier.h b/mozilla/layout/style/nsIStyleRuleSupplier.h
index 08278facaa9..45da063535a 100644
--- a/mozilla/layout/style/nsIStyleRuleSupplier.h
+++ b/mozilla/layout/style/nsIStyleRuleSupplier.h
@@ -20,6 +20,9 @@ class nsIStyleRuleSupplier : public nsISupports {
                        nsISupportsArrayEnumFunc aFunc, void* aData,
                        nsIContent* aContent)=0;
   NS_IMETHOD MatchesScopedRoot(nsIContent* aContent, PRBool* aResult)=0;
+
+  NS_IMETHOD AttributeAffectsStyle(nsISupportsArrayEnumFunc aFunc, void* aData, nsIContent* aContent,
+                                   PRBool* aAffects)=0;
 };
 
 #endif /* _nsIStyleRuleSupplier_h */
diff --git a/mozilla/layout/style/nsStyleSet.cpp b/mozilla/layout/style/nsStyleSet.cpp
index 8628adb3df8..9f30dfb1fd6 100644
--- a/mozilla/layout/style/nsStyleSet.cpp
+++ b/mozilla/layout/style/nsStyleSet.cpp
@@ -1937,15 +1937,22 @@ StyleSetImpl::AttributeAffectsStyle(nsIAtom *aAttribute, nsIContent *aContent,
   pair.attribute = aAttribute;
   pair.content = aContent;
 
-  /* check until we find a sheet that will be affected */
-  if ((mDocSheets && !mDocSheets->EnumerateForwards(EnumAffectsStyle, &pair)) ||
-      (mOverrideSheets && !mOverrideSheets->EnumerateForwards(EnumAffectsStyle,
-                                                              &pair)) ||
-      (mBackstopSheets && !mBackstopSheets->EnumerateForwards(EnumAffectsStyle,
-                                                              &pair))) {
-    aAffects = PR_TRUE;
-  } else {
-    aAffects = PR_FALSE;
+  /* scoped sheets should be checked first, since - if present - they will contain
+     the bulk of the applicable rules for the content node. */
+  if (mStyleRuleSupplier)
+    mStyleRuleSupplier->AttributeAffectsStyle(EnumAffectsStyle, &pair, aContent, &aAffects);
+
+  if (!aAffects) {
+    /* check until we find a sheet that will be affected */
+    if ((mDocSheets && !mDocSheets->EnumerateForwards(EnumAffectsStyle, &pair)) ||
+        (mOverrideSheets && !mOverrideSheets->EnumerateForwards(EnumAffectsStyle,
+                                                                &pair)) ||
+        (mBackstopSheets && !mBackstopSheets->EnumerateForwards(EnumAffectsStyle,
+                                                                &pair))) {
+      aAffects = PR_TRUE;
+    } else {
+      aAffects = PR_FALSE;
+    }
   }
 
   return NS_OK;