diff --git a/mozilla/layout/base/nsBidiPresUtils.cpp b/mozilla/layout/base/nsBidiPresUtils.cpp
index c0d017c2189..b8ee7042d9f 100644
--- a/mozilla/layout/base/nsBidiPresUtils.cpp
+++ b/mozilla/layout/base/nsBidiPresUtils.cpp
@@ -111,9 +111,7 @@ SplitInlineAncestors(nsPresContext* aPresContext,
   nsIFrame* newFrame = aFrame->GetNextSibling();
   nsIFrame* newParent;
 
-  while (nsLayoutAtoms::inlineFrame == parent->GetType() ||
-         nsLayoutAtoms::positionedInlineFrame == parent->GetType()) {
-
+  while (parent->IsFrameOfType(nsIFrame::eBidiInlineContainer)) {
     nsIFrame* grandparent = parent->GetParent();
     NS_ASSERTION(grandparent, "Couldn't get parent's parent in nsBidiPresUtils::SplitInlineAncestors");
     
@@ -449,16 +447,13 @@ nsBidiPresUtils::Resolve(nsPresContext* aPresContext,
       nsIFrame* child = frame;
       nsIFrame* parent = frame->GetParent();
       while (parent &&
-             (nsLayoutAtoms::inlineFrame == parent->GetType() ||
-              nsLayoutAtoms::positionedInlineFrame == parent->GetType()) &&
+             parent->IsFrameOfType(nsIFrame::eBidiInlineContainer) &&
              !child->GetNextSibling()) {
         child = parent;
         parent = child->GetParent();
       }
-      if (parent &&
-          (nsLayoutAtoms::inlineFrame == parent->GetType() ||
-           nsLayoutAtoms::positionedInlineFrame == parent->GetType()))
-        SplitInlineAncestors(aPresContext, child);      
+      if (parent && parent->IsFrameOfType(nsIFrame::eBidiInlineContainer))
+        SplitInlineAncestors(aPresContext, child);
     }
   } // for
   return mSuccess;
@@ -470,9 +465,7 @@ PRBool IsBidiLeaf(nsIFrame* aFrame) {
   nsIFrame* kid = aFrame->GetFirstChild(nsnull);
   return !kid
     || aFrame->GetStyleDisplay()->IsBlockLevel()
-    || !(nsLayoutAtoms::inlineFrame == frameType
-         || nsLayoutAtoms::positionedInlineFrame == frameType
-         || nsLayoutAtoms::letterFrame == frameType
+    || !(aFrame->IsFrameOfType(nsIFrame::eBidiInlineContainer)
          || nsLayoutAtoms::blockFrame == frameType);
 }
 
@@ -493,9 +486,9 @@ nsBidiPresUtils::InitLogicalArray(nsPresContext* aPresContext,
        frame && frame != aNextInFlow;
        frame = frame->GetNextSibling()) {
     directionalFrame = nsnull;
-    const nsStyleDisplay* display = frame->GetStyleDisplay();
 
-    if (aAddMarkers && !display->IsBlockLevel() ) {
+    if (aAddMarkers &&
+        frame->IsFrameOfType(nsIFrame::eBidiInlineContainer)) {
       const nsStyleVisibility* vis = frame->GetStyleVisibility();
       const nsStyleTextReset* text = frame->GetStyleTextReset();
       switch (text->mUnicodeBidi) {
diff --git a/mozilla/layout/generic/nsFirstLetterFrame.cpp b/mozilla/layout/generic/nsFirstLetterFrame.cpp
index 818bdeef4f5..41bde76f66e 100644
--- a/mozilla/layout/generic/nsFirstLetterFrame.cpp
+++ b/mozilla/layout/generic/nsFirstLetterFrame.cpp
@@ -64,6 +64,8 @@ public:
   NS_IMETHOD GetFrameName(nsAString& aResult) const;
 #endif
   virtual nsIAtom* GetType() const;
+  virtual PRBool IsFrameOfType(PRUint32 aFlags) const;
+
   NS_IMETHOD Reflow(nsPresContext*          aPresContext,
                     nsHTMLReflowMetrics&     aDesiredSize,
                     const nsHTMLReflowState& aReflowState,
@@ -105,6 +107,12 @@ nsFirstLetterFrame::GetType() const
   return nsLayoutAtoms::letterFrame;
 }
 
+PRBool
+nsFirstLetterFrame::IsFrameOfType(PRUint32 aFlags) const
+{
+  return !(aFlags & ~nsIFrame::eBidiInlineContainer);
+}
+
 PRIntn
 nsFirstLetterFrame::GetSkipSides() const
 {
diff --git a/mozilla/layout/generic/nsIFrame.h b/mozilla/layout/generic/nsIFrame.h
index a90b253b031..acc4e7996be 100644
--- a/mozilla/layout/generic/nsIFrame.h
+++ b/mozilla/layout/generic/nsIFrame.h
@@ -1174,9 +1174,10 @@ public:
    * Bit-flags to pass to IsFrameOfType()
    */
   enum {
-    eMathML =           1 << 0,
-    eSVG =              1 << 1,
-    eSVGForeignObject = 1 << 2
+    eMathML =              1 << 0,
+    eSVG =                 1 << 1,
+    eSVGForeignObject =    1 << 2,
+    eBidiInlineContainer = 1 << 3
   };
 
   /**
diff --git a/mozilla/layout/generic/nsInlineFrame.cpp b/mozilla/layout/generic/nsInlineFrame.cpp
index 198bd2c3c6a..e081517d446 100644
--- a/mozilla/layout/generic/nsInlineFrame.cpp
+++ b/mozilla/layout/generic/nsInlineFrame.cpp
@@ -105,6 +105,12 @@ nsInlineFrame::GetType() const
   return nsLayoutAtoms::inlineFrame;
 }
 
+PRBool
+nsInlineFrame::IsFrameOfType(PRUint32 aFlags) const
+{
+  return !(aFlags & ~nsIFrame::eBidiInlineContainer);
+}
+
 inline PRBool
 IsPaddingZero(nsStyleUnit aUnit, nsStyleCoord &aCoord)
 {
diff --git a/mozilla/layout/generic/nsInlineFrame.h b/mozilla/layout/generic/nsInlineFrame.h
index 28403b6cf2f..4d88af07294 100644
--- a/mozilla/layout/generic/nsInlineFrame.h
+++ b/mozilla/layout/generic/nsInlineFrame.h
@@ -108,6 +108,7 @@ public:
   NS_IMETHOD GetFrameName(nsAString& aResult) const;
 #endif
   virtual nsIAtom* GetType() const;
+  virtual PRBool IsFrameOfType(PRUint32 aFlags) const;
 
   virtual PRBool IsEmpty();
   virtual PRBool IsSelfEmpty();