Accelerated filters should filter unpadded primitives.

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

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 2225 matching lines @@
         // Reflections are implemented with Layers that hang off of the reflected layer. However,
         // the reflection layer subtree does not include the subtree of the parent Layer, so
         // a recursive computation of stacking children yields no results. This breaks cases when there are stacking
         // children of the parent, that need to be included in reflected composited bounds.
         // Fix this by including composited bounds of stacking children of the reflected Layer.
         if (hasCompositedLayerMapping() && parent() && parent()->reflectionInfo() && parent()->reflectionInfo()->reflectionLayer() == this)
             expandRectForReflectionAndStackingChildren(parent(), result);
         else
             expandRectForReflectionAndStackingChildren(this, result);
 
-        // FIXME: We can optimize the size of the composited layers, by not enlarging
-        // filtered areas with the outsets if we know that the filter is going to render in hardware.
-        // https://bugs.webkit.org/show_bug.cgi?id=81239
-        result.expand(filterOutsets());
+        // Only enlarge by the filter outsets if we know the filter is going to be rendered in software.
+        // Accelerated filters will handle their own outsets.
+        if (paintsWithFilters()) {
+            result.expand(filterOutsets());
+        }
     }
 
     if (transform() && paintsWithTransform(GlobalPaintNormalPhase) && (this != ancestorLayer || options == MaybeIncludeTransformForAncestorLayer))
         result = transform()->mapRect(result);
 
     if (enclosingPaginationLayer()) {
         convertFromFlowThreadToVisualBoundingBoxInAncestor(this, ancestorLayer, result);
         return result;
     }
     LayoutPoint delta;
@@ skipping 570 matching lines @@
 
 void showLayerTree(const blink::LayoutObject* layoutObject)
 {
     if (!layoutObject) {
         fprintf(stderr, "Cannot showLayerTree. Root is (nil)\n");
         return;
     }
     showLayerTree(layoutObject->enclosingLayer());
 }
 #endif