Replace filter outsets with bounds mapping in Blink.

third_party/WebKit/Source/core/paint/PaintLayer.h

Index: third_party/WebKit/Source/core/paint/PaintLayer.h
diff --git a/third_party/WebKit/Source/core/paint/PaintLayer.h b/third_party/WebKit/Source/core/paint/PaintLayer.h
index 2a28fab1e5e6925ffe7f4d3a4fbeb02656f76888..e52d05b8d0478c475d8dd5af1bff8996c44108d8 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.h
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.h
@@ -326,7 +326,7 @@ public:
 
     PaintLayer* enclosingLayerForPaintInvalidationCrossingFrameBoundaries() const;
 
-    bool hasAncestorWithFilterOutsets() const;
+    bool hasAncestorWithFilterThatMovesPixels() const;
 
     bool canUseConvertToLayerCoords() const
     {
@@ -469,8 +469,17 @@ public:
     bool paintsWithFilters() const;
     bool paintsWithBackdropFilters() const;
     FilterEffect* lastFilterEffect() const;
-    bool hasFilterOutsets() const;
-    FilterOutsets filterOutsets() const;
+
+    // Can map "forward" to determine which pixels in a destination rect are
+    // affected by pixels in the source rect, or "backward" to determine which
+    // pixels in the source rect are required for a destination rect.
+    // See also FilterEffect::mapRect.
+    FloatRect mapRectForFilter(const FloatRect&, bool forward = true) const;

[Stephen White, 2016/04/06 20:44:11]

I couldn't find any callsites that use forward "false". If so, could you remove
the param? If you really think you'll need it, you can always add it later.

[jbroman, 2016/04/06 21:51:41]

Alright, done.

+
+    // Calls the above, rounding outwards.
+    LayoutRect mapRectForFilter(const LayoutRect&, bool forward = true) const;

[Stephen White, 2016/04/06 20:44:11]

Naming nit: could we call this one mapLayoutRectForFilter(), just to be clear?

[jbroman, 2016/04/06 21:51:41]

Done.

+
+    bool hasFilterThatMovesPixels() const;
 
     PaintLayerFilterInfo* filterInfo() const { return m_rareData ? m_rareData->filterInfo.get() : nullptr; }
     PaintLayerFilterInfo& ensureFilterInfo();