Various doc cleanups

Issue #6439958  More R.attr breakage
Issue #918412  android.graphics.Paint.FontMetricsInt fields & methods need doc
Issue #917387  javadoc bug: Canvas.EdgeType has minimal documentation
Issue #18948460 [DAC-bug] LinearLayout xml layout_weight parameter is missing description

Change-Id: Idb289ca778b3f316923757405460031ce7a5e1e9