diff --git a/mozilla/layout/base/public/nsIFrame.h b/mozilla/layout/base/public/nsIFrame.h
index 749353c805f..dc08f38859d 100644
--- a/mozilla/layout/base/public/nsIFrame.h
+++ b/mozilla/layout/base/public/nsIFrame.h
@@ -580,7 +580,7 @@ public:
    * Get the style data associated with this frame.
    */
   NS_IMETHOD GetStyleDataExternal(nsStyleStructID aSID,
-                                  const nsStyleStruct*& aStyleStruct) = 0;
+                                  const nsStyleStruct*& aStyleStruct) const = 0;
 
 #ifdef _IMPL_NS_LAYOUT
   nsresult GetStyleData(nsStyleStructID       aSID,
@@ -591,7 +591,7 @@ public:
   }
 #else
   nsresult GetStyleData(nsStyleStructID       aSID,
-                        const nsStyleStruct*& aStyleStruct) {
+                        const nsStyleStruct*& aStyleStruct) const {
     return GetStyleDataExternal(aSID, aStyleStruct);
   }
 #endif
diff --git a/mozilla/layout/generic/nsFrame.cpp b/mozilla/layout/generic/nsFrame.cpp
index b32a0688afd..d43f8152e96 100644
--- a/mozilla/layout/generic/nsFrame.cpp
+++ b/mozilla/layout/generic/nsFrame.cpp
@@ -4716,7 +4716,7 @@ nsFrame::GetProperty(nsIPresContext* aPresContext,
 
 NS_IMETHODIMP
 nsFrame::GetStyleDataExternal(nsStyleStructID aSID,
-                              const nsStyleStruct*& aStyleStruct)
+                              const nsStyleStruct*& aStyleStruct) const
 {
   if (!mStyleContext) {
     aStyleStruct = nsnull;
diff --git a/mozilla/layout/generic/nsFrame.h b/mozilla/layout/generic/nsFrame.h
index 9c7b32a4bc5..69579b87143 100644
--- a/mozilla/layout/generic/nsFrame.h
+++ b/mozilla/layout/generic/nsFrame.h
@@ -398,7 +398,7 @@ public:
                                NSFramePropertyDtorFunc aPropDtorFunc);
 
   NS_IMETHOD GetStyleDataExternal(nsStyleStructID aSID,
-                                  const nsStyleStruct*& aStyleStruct);
+                                  const nsStyleStruct*& aStyleStruct) const;
 
 #ifdef IBMBIDI
   NS_IMETHOD GetBidiProperty(nsIPresContext* aPresContext,
diff --git a/mozilla/layout/generic/nsIFrame.h b/mozilla/layout/generic/nsIFrame.h
index 749353c805f..dc08f38859d 100644
--- a/mozilla/layout/generic/nsIFrame.h
+++ b/mozilla/layout/generic/nsIFrame.h
@@ -580,7 +580,7 @@ public:
    * Get the style data associated with this frame.
    */
   NS_IMETHOD GetStyleDataExternal(nsStyleStructID aSID,
-                                  const nsStyleStruct*& aStyleStruct) = 0;
+                                  const nsStyleStruct*& aStyleStruct) const = 0;
 
 #ifdef _IMPL_NS_LAYOUT
   nsresult GetStyleData(nsStyleStructID       aSID,
@@ -591,7 +591,7 @@ public:
   }
 #else
   nsresult GetStyleData(nsStyleStructID       aSID,
-                        const nsStyleStruct*& aStyleStruct) {
+                        const nsStyleStruct*& aStyleStruct) const {
     return GetStyleDataExternal(aSID, aStyleStruct);
   }
 #endif
diff --git a/mozilla/layout/html/base/src/nsFrame.cpp b/mozilla/layout/html/base/src/nsFrame.cpp
index b32a0688afd..d43f8152e96 100644
--- a/mozilla/layout/html/base/src/nsFrame.cpp
+++ b/mozilla/layout/html/base/src/nsFrame.cpp
@@ -4716,7 +4716,7 @@ nsFrame::GetProperty(nsIPresContext* aPresContext,
 
 NS_IMETHODIMP
 nsFrame::GetStyleDataExternal(nsStyleStructID aSID,
-                              const nsStyleStruct*& aStyleStruct)
+                              const nsStyleStruct*& aStyleStruct) const
 {
   if (!mStyleContext) {
     aStyleStruct = nsnull;
diff --git a/mozilla/layout/html/base/src/nsFrame.h b/mozilla/layout/html/base/src/nsFrame.h
index 9c7b32a4bc5..69579b87143 100644
--- a/mozilla/layout/html/base/src/nsFrame.h
+++ b/mozilla/layout/html/base/src/nsFrame.h
@@ -398,7 +398,7 @@ public:
                                NSFramePropertyDtorFunc aPropDtorFunc);
 
   NS_IMETHOD GetStyleDataExternal(nsStyleStructID aSID,
-                                  const nsStyleStruct*& aStyleStruct);
+                                  const nsStyleStruct*& aStyleStruct) const;
 
 #ifdef IBMBIDI
   NS_IMETHOD GetBidiProperty(nsIPresContext* aPresContext,