Skip paint chunks with effectively invisible opacity.

third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp

Index: third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
index 2d0b917413a35611db9079fff8995dca642b36f9..f1973e3f2da2bde979896f66abc627cf289269be 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
@@ -64,43 +64,6 @@ static ShouldRespectOverflowClipType ShouldRespectOverflowClip(
              : kRespectOverflowClip;
 }
 
-bool PaintLayerPainter::PaintedOutputInvisible(

[chrishtr, 2017/04/26 19:58:21]

I think we still need this for SPv1.

[wkorman, 2017/04/27 00:02:32]

Restored SPv1 behavior.

-    const PaintLayerPaintingInfo& painting_info) {
-  const LayoutObject& layout_object = paint_layer_.GetLayoutObject();
-  if (layout_object.HasBackdropFilter())
-    return false;
-
-  // Always paint when 'will-change: opacity' is present. Reduces jank for
-  // common animation implementation approaches, for example, an element that
-  // starts with opacity zero and later begins to animate.
-  if (layout_object.StyleRef().HasWillChangeOpacityHint())
-    return false;
-
-  if (RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
-    if (layout_object.StyleRef().Opacity())
-      return false;
-
-    const EffectPaintPropertyNode* effect =
-        layout_object.PaintProperties()->Effect();
-    if (effect && effect->RequiresCompositingForAnimation()) {
-      return false;
-    }
-  }
-
-  // 0.0004f < 1/2048. With 10-bit color channels (only available on the
-  // newest Macs; otherwise it's 8-bit), we see that an alpha of 1/2048 or
-  // less leads to a color output of less than 0.5 in all channels, hence
-  // not visible.
-  static const float kMinimumVisibleOpacity = 0.0004f;
-  if (paint_layer_.PaintsWithTransparency(
-          painting_info.GetGlobalPaintFlags())) {
-    if (layout_object.StyleRef().Opacity() < kMinimumVisibleOpacity) {
-      return true;
-    }
-  }
-  return false;
-}
-
 PaintResult PaintLayerPainter::Paint(
     GraphicsContext& context,
     const PaintLayerPaintingInfo& painting_info,
@@ -135,10 +98,6 @@ PaintResult PaintLayerPainter::Paint(
           ->ShouldThrottleRendering())
     return kFullyPainted;
 
-  // If this layer is totally invisible then there is nothing to paint.
-  if (PaintedOutputInvisible(painting_info))
-    return kFullyPainted;
-
   if (paint_layer_.PaintsWithTransparency(painting_info.GetGlobalPaintFlags()))
     paint_flags |= kPaintLayerHaveTransparency;