Change the bulk of ascent (baseline) computation to happen on a virtual method on nsIFrame, and remove the redundant descent member from nsHTMLReflowMetrics, primarily to support having both first-line and last-line baselines. b=367332 r+sr=roc

git-svn-id: svn://10.0.0.236/trunk@218785 18797224-902f-48f8-a5cc-f745e15eee43

mozilla/layout/generic/nsImageFrame.cpp

@@ -881,8 +881,6 @@ nsImageFrame::Reflow(nsPresContext*          aPresContext,
       aStatus = NS_FRAME_NOT_COMPLETE;
     }
   }
-  aMetrics.ascent  = aMetrics.height;
-  aMetrics.descent = 0;
 
   aMetrics.mOverflowArea.SetRect(0, 0, aMetrics.width, aMetrics.height);
   FinishAndStoreOverflow(&aMetrics);