b=23707. Made sure HR frame correctly computes max-element-size

when it has an 'auto' width

layout/html/base/src/nsHRFrame.cpp

@@ -230,9 +230,10 @@ HRuleFrame::Reflow(nsIPresContext*          aPresContext,
   if (nsnull != aDesiredSize.maxElementSize) {
     nscoord onePixel = NSIntPixelsToTwips(1, p2t);
     if (NS_UNCONSTRAINEDSIZE != aReflowState.mComputedWidth) {
-      if (eStyleUnit_Percent ==
-          aReflowState.mStylePosition->mWidth.GetUnit()) {
-        // When the HR is using a percentage width, make sure it
+      nsStyleUnit widthUnit = aReflowState.mStylePosition->mWidth.GetUnit();
+      if ((eStyleUnit_Percent == widthUnit) || 
+          (eStyleUnit_Auto == widthUnit)) {
+        // When the HR is using an 'auto' or percentage width, make sure it
         // remains springy.
         aDesiredSize.maxElementSize->width = onePixel;
       }

layout/html/table/src/nsTableRowFrame.cpp

@@ -1278,7 +1278,7 @@ NS_METHOD nsTableRowFrame::IR_TargetIsChild(nsIPresContext*      aPresContext,
         // layout strategy will compute a different maximum content width than we
         // computed for the initial reflow. That's because the table layout
         // strategy doesn't check whether the cell is auto-width...
-        desiredSize.mMaximumWidth = desiredSize.width;
+        desiredSize.mMaximumWidth = PR_MIN(desiredSize.mMaximumWidth, desiredSize.width);
       }
       ((nsTableCellFrame *)aNextFrame)->SetMaximumWidth(desiredSize.mMaximumWidth);
       if (oldMaximumWidth != desiredSize.mMaximumWidth) {

layout/tables/nsTableRowFrame.cpp

@@ -1278,7 +1278,7 @@ NS_METHOD nsTableRowFrame::IR_TargetIsChild(nsIPresContext*      aPresContext,
         // layout strategy will compute a different maximum content width than we
         // computed for the initial reflow. That's because the table layout
         // strategy doesn't check whether the cell is auto-width...
-        desiredSize.mMaximumWidth = desiredSize.width;
+        desiredSize.mMaximumWidth = PR_MIN(desiredSize.mMaximumWidth, desiredSize.width);
       }
       ((nsTableCellFrame *)aNextFrame)->SetMaximumWidth(desiredSize.mMaximumWidth);
       if (oldMaximumWidth != desiredSize.mMaximumWidth) {