Commits on Oct 17, 2017

1. Switch box-shadows to use brush masks (and add basic brush prim). …

   This introduces a new brush primitive type. Right now, this is
   extremely basic and doesn't provide much new functionality. As
   more items are ported to use it, the functionality of the brush
   shader type will expand (mostly the VS parts).
   
   The major change in this patch is to remove the old box-shadow
   shader and switch box shadows to be drawn via a brush mask +
   gaussian blur approach.
   
   This *is* a performance regression for small / simple box shadows
   compared to previously, but this is only temporary. The goal of
   this (large) patch is to switch over to a different box-shadow
   technique and address correctness issues first, and then we can
   apply a number of optimizations on top of that. It *is* a performance
   win on very large box shadows, which was the performance worst
   case for the previous box shadow shader.
   
   The changes included:
    * Extend blur shader to support both A8 and RGBA8 blurs.
    * Basic brush shader and primitive code.
    * Brush mask shader.
    * Remove old box shadow shader.
    * Move some common clip functions to ellipse.glsl.
    * Extend cache image shader to support both A8 and RGBA8 sources.
    * Support clip masks in cache image shader.
    * Remove box shadow primitive type.
    * Add reftests for spread, offset, blur, border radius box-shadow variations.
    * Support adjusting the border radii of box shadows as defined by spec.
   
   Next steps:
    * Extend the mask shader to support arbitrary border radii per corner.
    * Apply various optimizations to the brush and blur code.

   

   gw3583 committed Oct 17, 2017

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