WebView-based subtitle styling doesn't render EDGE_TYPE_OUTLINE correctly

[icbaker]

Copying from #2194 (comment):

If I use the webview by subView.setViewType(SubtitleView.VIEW_TYPE_WEB) , the Arabic comma appears at the correct place. But in this mode, the subtitle's style is unruly. For example, CaptionStyleCompat.EDGE_TYPE_OUTLINE the outline is oddly,

I can reproduce this in 2.17.1 (screenshots below), using the "TTML positioning" sample and the following patch to the demo app in PlayerActivity#onCreate:

    playerView.getSubtitleView().setViewType(SubtitleView.VIEW_TYPE_WEB);
    playerView.getSubtitleView().setStyle(new CaptionStyleCompat(
        /* foregroundColor= */ Color.RED,
        /* backgroundColor= */ Color.GREEN,
        /* windowColor= */ Color.CYAN,
        CaptionStyleCompat.EDGE_TYPE_OUTLINE,
        /* edgeColor= */ Color.BLACK,
        /* typeface= */ null
    ));

Outline screenshots

Canvas

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WebView