diff --git a/widget/src/cocoa/nsNativeThemeCocoa.mm b/widget/src/cocoa/nsNativeThemeCocoa.mm
index 7cf3d76f785..b25e1d18ae4 100644
--- a/widget/src/cocoa/nsNativeThemeCocoa.mm
+++ b/widget/src/cocoa/nsNativeThemeCocoa.mm
@@ -719,6 +719,18 @@ nsNativeThemeCocoa::DrawButton(CGContextRef cgContext, ThemeButtonKind inKind,
       // leave things alone on Tiger
       drawFrame.size.height -= 1;
     }
+  } else if (inKind == kThemeListHeaderButton) {
+    CGContextClipToRect(cgContext, inBoxRect);
+    // Always remove the top border.
+    drawFrame.origin.y -= 1;
+    drawFrame.size.height += 1;
+    // Remove the left border in LTR mode and the right border in RTL mode.
+    drawFrame.size.width += 1;
+    PRBool isLast = IsLastTreeHeaderCell(aFrame);
+    if (isLast)
+      drawFrame.size.width += 1; // Also remove the other border.
+    if (!IsFrameRTL(aFrame) || isLast)
+      drawFrame.origin.x -= 1;
   }
 
   if (!needsScaling) {
@@ -1461,7 +1473,7 @@ nsNativeThemeCocoa::DrawWidgetBackground(nsIRenderingContext* aContext, nsIFrame
       TreeSortDirection sortDirection = GetTreeSortDirection(aFrame);
       DrawButton(cgContext, kThemeListHeaderButton, macRect, PR_FALSE, IsDisabled(aFrame), 
                  sortDirection == eTreeSortDirection_Natural ? kThemeButtonOff : kThemeButtonOn,
-                 sortDirection == eTreeSortDirection_Descending ?
+                 sortDirection == eTreeSortDirection_Ascending ?
                  kThemeAdornmentHeaderButtonSortUp : kThemeAdornmentNone, eventState, aFrame);      
     }
       break;
@@ -1817,7 +1829,7 @@ nsNativeThemeCocoa::GetMinimumWidgetSize(nsIRenderingContext* aContext,
     {
       SInt32 headerHeight = 0;
       ::GetThemeMetric(kThemeMetricListHeaderHeight, &headerHeight);
-      aResult->SizeTo(0, headerHeight);
+      aResult->SizeTo(0, headerHeight - 1); // We don't need the top border.
       break;
     }
 
diff --git a/widget/src/windows/nsNativeThemeWin.cpp b/widget/src/windows/nsNativeThemeWin.cpp
index c8309ee1afd..3a8e41f3acb 100644
--- a/widget/src/windows/nsNativeThemeWin.cpp
+++ b/widget/src/windows/nsNativeThemeWin.cpp
@@ -168,11 +168,6 @@ static SIZE GetGutterSize(HANDLE theme, HDC hdc)
     return ret;
 }
 
-static inline PRBool IsFrameRTL(nsIFrame *frame)
-{
-  return frame->GetStyleVisibility()->mDirection == NS_STYLE_DIRECTION_RTL;
-}
-
 static HRESULT DrawThemeBGRTLAware(HANDLE theme, HDC hdc, int part, int state,
                                    const RECT *widgetRect, const RECT *clipRect,
                                    PRBool isRTL)
diff --git a/widget/src/xpwidgets/nsNativeTheme.cpp b/widget/src/xpwidgets/nsNativeTheme.cpp
index c7e441358ff..352991f4658 100644
--- a/widget/src/xpwidgets/nsNativeTheme.cpp
+++ b/widget/src/xpwidgets/nsNativeTheme.cpp
@@ -169,6 +169,12 @@ nsNativeTheme::IsWidgetStyled(nsPresContext* aPresContext, nsIFrame* aFrame,
                                                NS_AUTHOR_SPECIFIED_BACKGROUND);
 }
 
+PRBool
+nsNativeTheme::IsFrameRTL(nsIFrame* aFrame)
+{
+  return aFrame && aFrame->GetStyleVisibility()->mDirection == NS_STYLE_DIRECTION_RTL;
+}
+
 // scrollbar button:
 PRInt32
 nsNativeTheme::GetScrollbarButtonType(nsIFrame* aFrame)
@@ -212,6 +218,34 @@ nsNativeTheme::GetTreeSortDirection(nsIFrame* aFrame)
   return eTreeSortDirection_Natural;
 }
 
+PRBool
+nsNativeTheme::IsLastTreeHeaderCell(nsIFrame* aFrame)
+{
+  if (!aFrame)
+    return PR_FALSE;
+
+  // A tree column picker is always the last header cell.
+  if (aFrame->GetContent()->Tag() == nsWidgetAtoms::treecolpicker)
+    return PR_TRUE;
+
+  // Find the parent tree.
+  nsIContent* parent = aFrame->GetContent()->GetParent();
+  while (parent && parent->Tag() != nsWidgetAtoms::tree) {
+    parent = parent->GetParent();
+  }
+
+  // If the column picker is visible, this can't be the last column.
+  if (parent && !parent->AttrValueIs(kNameSpaceID_None, nsWidgetAtoms::hidecolumnpicker,
+                                     NS_LITERAL_STRING("true"), eCaseMatters))
+    return PR_FALSE;
+
+  while ((aFrame = aFrame->GetNextSibling())) {
+    if (aFrame->GetRect().width > 0)
+      return PR_FALSE;
+  }
+  return PR_TRUE;
+}
+
 // tab:
 PRBool
 nsNativeTheme::IsBottomTab(nsIFrame* aFrame)
diff --git a/widget/src/xpwidgets/nsNativeTheme.h b/widget/src/xpwidgets/nsNativeTheme.h
index 3e5495a1fe7..4070093436e 100644
--- a/widget/src/xpwidgets/nsNativeTheme.h
+++ b/widget/src/xpwidgets/nsNativeTheme.h
@@ -85,6 +85,9 @@ class nsNativeTheme
     return CheckBooleanAttr(aFrame, nsWidgetAtoms::disabled);
   }
 
+  // RTL chrome direction
+  PRBool IsFrameRTL(nsIFrame* aFrame);
+
   // button:
   PRBool IsDefaultButton(nsIFrame* aFrame) {
     return CheckBooleanAttr(aFrame, nsWidgetAtoms::_default);
@@ -119,6 +122,7 @@ class nsNativeTheme
 
   // treeheadercell:
   TreeSortDirection GetTreeSortDirection(nsIFrame* aFrame);
+  PRBool IsLastTreeHeaderCell(nsIFrame* aFrame);
 
   // tab:
   PRBool IsBottomTab(nsIFrame* aFrame);
diff --git a/widget/src/xpwidgets/nsWidgetAtomList.h b/widget/src/xpwidgets/nsWidgetAtomList.h
index 6f103a16ff5..1549da09bb8 100644
--- a/widget/src/xpwidgets/nsWidgetAtomList.h
+++ b/widget/src/xpwidgets/nsWidgetAtomList.h
@@ -77,6 +77,7 @@ WIDGET_ATOM(focused, "focused")
 WIDGET_ATOM(Forward, "Forward")
 WIDGET_ATOM(Home, "Home")
 WIDGET_ATOM(hidden, "hidden")
+WIDGET_ATOM(hidecolumnpicker, "hidecolumnpicker")
 WIDGET_ATOM(horizontal, "horizontal")
 WIDGET_ATOM(vertical, "vertical")
 WIDGET_ATOM(id, "id")
@@ -118,6 +119,8 @@ WIDGET_ATOM(state, "state")
 WIDGET_ATOM(step, "step")
 WIDGET_ATOM(Stop, "Stop")
 WIDGET_ATOM(_true, "true")
+WIDGET_ATOM(tree, "tree")
+WIDGET_ATOM(treecolpicker, "treecolpicker")
 WIDGET_ATOM(type, "type")
 WIDGET_ATOM(value, "value")