--- a/layout/style/nsCSSAnonBoxList.h
+++ b/layout/style/nsCSSAnonBoxList.h
@@ -128,17 +128,16 @@ CSS_WRAPPER_ANON_BOX(rubyText, ":-moz-ru
 CSS_WRAPPER_ANON_BOX(rubyTextContainer, ":-moz-ruby-text-container")
 
 #ifdef MOZ_XUL
 CSS_ANON_BOX(mozTreeColumn, ":-moz-tree-column")
 CSS_ANON_BOX(mozTreeRow, ":-moz-tree-row")
 CSS_ANON_BOX(mozTreeSeparator, ":-moz-tree-separator")
 CSS_ANON_BOX(mozTreeCell, ":-moz-tree-cell")
 CSS_ANON_BOX(mozTreeIndentation, ":-moz-tree-indentation")
-CSS_ANON_BOX(mozTreeLine, ":-moz-tree-line")
 CSS_ANON_BOX(mozTreeTwisty, ":-moz-tree-twisty")
 CSS_ANON_BOX(mozTreeImage, ":-moz-tree-image")
 CSS_ANON_BOX(mozTreeCellText, ":-moz-tree-cell-text")
 CSS_ANON_BOX(mozTreeCheckbox, ":-moz-tree-checkbox")
 CSS_ANON_BOX(mozTreeDropFeedback, ":-moz-tree-drop-feedback")
 #endif
 
 CSS_ANON_BOX(mozSVGMarkerAnonChild, ":-moz-svg-marker-anon-child")

--- a/layout/xul/tree/nsTreeBodyFrame.cpp
+++ b/layout/xul/tree/nsTreeBodyFrame.cpp
@@ -3232,101 +3232,16 @@ nsTreeBodyFrame::PaintCell(int32_t      
 
     int32_t level;
     mView->GetLevel(aRowIndex, &level);
 
     if (!isRTL)
       currX += mIndentation * level;
     remainingWidth -= mIndentation * level;
 
-    // Resolve the style to use for the connecting lines.
-    ComputedStyle* lineContext = GetPseudoComputedStyle(nsCSSAnonBoxes::mozTreeLine);
-
-    if (mIndentation && level &&
-        lineContext->StyleVisibility()->IsVisibleOrCollapsed()) {
-      // Paint the thread lines.
-
-      // Get the size of the twisty. We don't want to paint the twisty
-      // before painting of connecting lines since it would paint lines over
-      // the twisty. But we need to leave a place for it.
-      ComputedStyle* twistyContext = GetPseudoComputedStyle(nsCSSAnonBoxes::mozTreeTwisty);
-
-      nsRect imageSize;
-      nsRect twistyRect(aCellRect);
-      GetTwistyRect(aRowIndex, aColumn, imageSize, twistyRect, aPresContext,
-                    twistyContext);
-
-      nsMargin twistyMargin;
-      twistyContext->StyleMargin()->GetMargin(twistyMargin);
-      twistyRect.Inflate(twistyMargin);
-
-      const nsStyleBorder* borderStyle = lineContext->StyleBorder();
-      // Resolve currentcolor values against the treeline context
-      nscolor color = borderStyle->mBorderLeftColor.CalcColor(lineContext);
-      ColorPattern colorPatt(ToDeviceColor(color));
-
-      uint8_t style = borderStyle->GetBorderStyle(eSideLeft);
-      StrokeOptions strokeOptions;
-      nsLayoutUtils::InitDashPattern(strokeOptions, style);
-
-      nscoord srcX = currX + twistyRect.width - mIndentation / 2;
-      nscoord lineY = (aRowIndex - mTopRowIndex) * mRowHeight + aPt.y;
-
-      DrawTarget* drawTarget = aRenderingContext.GetDrawTarget();
-      nsPresContext* pc = PresContext();
-
-      // Don't paint off our cell.
-      if (srcX <= cellRect.x + cellRect.width) {
-        nscoord destX = currX + twistyRect.width;
-        if (destX > cellRect.x + cellRect.width)
-          destX = cellRect.x + cellRect.width;
-        if (isRTL) {
-          srcX = currX + remainingWidth - (srcX - cellRect.x);
-          destX = currX + remainingWidth - (destX - cellRect.x);
-        }
-        Point p1(pc->AppUnitsToGfxUnits(srcX),
-                 pc->AppUnitsToGfxUnits(lineY + mRowHeight / 2));
-        Point p2(pc->AppUnitsToGfxUnits(destX),
-                 pc->AppUnitsToGfxUnits(lineY + mRowHeight / 2));
-        SnapLineToDevicePixelsForStroking(p1, p2, *drawTarget,
-                                          strokeOptions.mLineWidth);
-        drawTarget->StrokeLine(p1, p2, colorPatt, strokeOptions);
-      }
-
-      int32_t currentParent = aRowIndex;
-      for (int32_t i = level; i > 0; i--) {
-        if (srcX <= cellRect.x + cellRect.width) {
-          // Paint full vertical line only if we have next sibling.
-          bool hasNextSibling;
-          mView->HasNextSibling(currentParent, aRowIndex, &hasNextSibling);
-          if (hasNextSibling || i == level) {
-            Point p1(pc->AppUnitsToGfxUnits(srcX),
-                     pc->AppUnitsToGfxUnits(lineY));
-            Point p2;
-            p2.x = pc->AppUnitsToGfxUnits(srcX);
-
-            if (hasNextSibling)
-              p2.y = pc->AppUnitsToGfxUnits(lineY + mRowHeight);
-            else if (i == level)
-              p2.y = pc->AppUnitsToGfxUnits(lineY + mRowHeight / 2);
-
-            SnapLineToDevicePixelsForStroking(p1, p2, *drawTarget,
-                                              strokeOptions.mLineWidth);
-            drawTarget->StrokeLine(p1, p2, colorPatt, strokeOptions);
-          }
-        }
-
-        int32_t parent;
-        if (NS_FAILED(mView->GetParentIndex(currentParent, &parent)) || parent < 0)
-          break;
-        currentParent = parent;
-        srcX -= mIndentation;
-      }
-    }
-
     // Always leave space for the twisty.
     nsRect twistyRect(currX, cellRect.y, remainingWidth, cellRect.height);
     result &= PaintTwisty(aRowIndex, aColumn, twistyRect, aPresContext,
                           aRenderingContext, aDirtyRect, remainingWidth,
                           currX);
   }
 
   // Now paint the icon for our cell.

--- a/security/manager/pki/resources/content/certViewer.xul
+++ b/security/manager/pki/resources/content/certViewer.xul
@@ -129,17 +129,17 @@
               hidecolumnpicker="true" style="height: 8em;">
           <treecols>
             <treecol id="dumpCol" flex="1" primary="true" hideheader="true"/>
           </treecols>
         </tree>
 
         <label class="header" value="&certmgr.details.label;"
                control="prettyDumpTree" accesskey="&certmgr.details.accesskey;"/>
-        <tree id="prettyDumpTree" style="height: 15em" treelines="true" flex="1"
+        <tree id="prettyDumpTree" style="height: 15em" flex="1"
                   onselect="displaySelected();" hidecolumnpicker="true">
           <treecols>
             <treecol flex="1" id="certDataCol" primary="true" hideheader="true"/>
           </treecols>
           <treechildren/>
         </tree>
 
         <label class="header" value="&certmgr.fields.label;"

--- a/toolkit/content/xul.css
+++ b/toolkit/content/xul.css
@@ -631,21 +631,16 @@ treecol[hidden="true"] {
   display: -moz-box;
 }
 
 .tree-scrollable-columns {
   /* Yes, Virginia, this makes it scrollable */
   overflow: hidden;
 }
 
-/* ::::: lines connecting cells ::::: */
-tree:not([treelines="true"]) > treechildren::-moz-tree-line {
-  visibility: hidden;
-}
-
 treechildren::-moz-tree-cell(ltr) {
   direction: ltr !important;
 }
 
 /********** deck & stack *********/
 
 deck {
   display: -moz-deck;

--- a/toolkit/themes/linux/global/tree.css
+++ b/toolkit/themes/linux/global/tree.css
@@ -131,30 +131,16 @@ tree[seltype="text"] > treechildren::-mo
 tree[seltype="cell"] > treechildren::-moz-tree-cell(active, selected, current, focus) {
   border: 1px dotted #C0C0C0;
 }
 
 tree[seltype="text"] > treechildren::-moz-tree-cell-text(active, selected, current, focus) {
   border: 1px dotted #C0C0C0;
 }
 
-/* ::::: lines connecting cells ::::: */
-
-tree[seltype="cell"] > treechildren::-moz-tree-line,
-tree[seltype="text"] > treechildren::-moz-tree-line,
-treechildren::-moz-tree-line {
-  border: 1px dotted ThreeDShadow;
-}
-
-tree[seltype="cell"] > treechildren::-moz-tree-line(active, selected, focus),
-treechildren::-moz-tree-line(selected, focus) {
-  border: 1px dotted HighlightText;
-}
-
-
 /* ::::: tree separator ::::: */
 
 treechildren::-moz-tree-separator {
   border-top: 1px solid ThreeDShadow;
   border-bottom: 1px solid ThreeDHighlight;
 }
 
 

--- a/toolkit/themes/osx/global/tree.css
+++ b/toolkit/themes/osx/global/tree.css
@@ -98,27 +98,16 @@ tree[seltype="cell"] > treechildren::-mo
   color: HighlightText;
 }
 
 tree[seltype="text"] > treechildren::-moz-tree-cell-text(active, selected, focus) {
   background-color: Highlight;
   color: HighlightText;
 }
 
-/* ::::: lines connecting cells ::::: */
-
-treechildren::-moz-tree-line {
-  /* XXX there should be no border on Mac, but trees currently
-         paint the line black by default, so I'll just leave this
-         for now. */
-  visibility: hidden;
-  border: 1px dotted grey;
-}
-
-
 /* ::::: tree separator ::::: */
 
 treechildren::-moz-tree-separator {
   border-top: 1px dashed #C7C7C7;
   margin: 0 2px;
 }
 
 

--- a/toolkit/themes/windows/global/tree.css
+++ b/toolkit/themes/windows/global/tree.css
@@ -128,29 +128,16 @@ tree[seltype="text"] > treechildren::-mo
 tree[seltype="cell"] > treechildren::-moz-tree-cell(active, selected, current, focus) {
   border: 1px dotted #C0C0C0;
 }
 
 tree[seltype="text"] > treechildren::-moz-tree-cell-text(active, selected, current, focus) {
   border: 1px dotted #C0C0C0;
 }
 
-/* ::::: lines connecting cells ::::: */
-
-tree[seltype="cell"] > treechildren::-moz-tree-line,
-tree[seltype="text"] > treechildren::-moz-tree-line,
-treechildren::-moz-tree-line {
-  border: 1px dotted ThreeDShadow;
-}
-
-tree[seltype="cell"] > treechildren::-moz-tree-line(active, selected, focus),
-treechildren::-moz-tree-line(selected, focus) {
-  border: 1px dotted HighlightText;
-}
-
 /* ::::: tree separator ::::: */
 
 treechildren::-moz-tree-separator {
   border-top: 1px solid ThreeDShadow;
   border-bottom: 1px solid ThreeDHighlight;
 }