There's no reason for RenderLayerStackingNode::collectLayers to call updateDescendantDependentFlags

RenderLayerStackingNode::collectLayers doesn't read any descendant-dependent
information.

Review URL: https://codereview.chromium.org/345183002

git-svn-id: svn://svn.chromium.org/blink/trunk@176639 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Have GlyphBuffer track vertical advances and pass this to Skia.

This is quicker than having Skia figure it out after the fact, since we
already know in the simple text path that there are no vertical advances
(and so drawPosTextH can be safely used).

BUG=387166

Review URL: https://codereview.chromium.org/335293008

git-svn-id: svn://svn.chromium.org/blink/trunk@176640 bbb929c8-8fbe-4397-9dbb-9b2b20218538