Remove the SVG paint culling optimization

Source/core/rendering/svg/SVGRenderSupport.cpp

Index: Source/core/rendering/svg/SVGRenderSupport.cpp
diff --git a/Source/core/rendering/svg/SVGRenderSupport.cpp b/Source/core/rendering/svg/SVGRenderSupport.cpp
index 0b8824d99480e80df204f12997c49dd676921fb3..8f2c9c5afc9859291b7fede1e24e6426a8059e16 100644
--- a/Source/core/rendering/svg/SVGRenderSupport.cpp
+++ b/Source/core/rendering/svg/SVGRenderSupport.cpp
@@ -145,6 +145,22 @@ const RenderObject* SVGRenderSupport::pushMappingToContainer(const RenderObject*
     return parent;
 }
 
+const AffineTransform SVGRenderSupport::transformToRootBorderBox(const RenderObject& renderer, const AffineTransform& localTransform)
+{
+    AffineTransform transform = localTransform;
+    RenderObject* next = renderer.parent();
+    while (next && !next->isSVGRoot()) {

[pdr., 2014/12/15 05:02:21]

linear algebra 101: instead of inverting each matrix, we can post-multiply them
in reverse and invert the result.

[fs, 2014/12/15 10:28:16]

If next is/ends up as null, you'll be toast anyway.

[pdr., 2014/12/18 22:22:40]

Replaced with an assert.

+        transform = next->localToParentTransform() * transform;

[fs, 2014/12/15 10:28:16]

(Last I checked a sequence like this generated horrible code... lots of copies.
Wanted (DoA - preferably A): multiply-from-the-left method on AffineTransform.)

[pdr., 2014/12/16 06:29:56]

It does indeed, we should add this to AffineTransform next time we need it.

[pdr., 2014/12/18 22:22:40]

I looked into this and premultiply doesn't seem as expensive as I remembered. We
do create a copy for each walk up the parent chain but AffineTransform is cheap
to copy. I did file http://crbug.com/443775 for some other AffineTransform
optimization ideas though.

[fs, 2014/12/19 11:46:00]

Moves are cheap execution-wise, but cost in terms of decoder resources (and
code-size).

+        next = next->parent();
+    }
+    transform = toRenderSVGRoot(next)->localToBorderBoxTransform() * transform;
+
+    if (!transform.isInvertible())

[fs, 2014/12/15 10:28:16]

Maybe just return |transform| instead of its inverse? The name doesn't really
help imply one or the other; see also issue at callsite. Also, IIRC inverse()
gives you this behavior by default (det == 0 => identify else ...)

+        return AffineTransform();
+
+    return transform.inverse();
+}
+
 // Update a bounding box taking into account the validity of the other bounding box.
 inline void SVGRenderSupport::updateObjectBoundingBox(FloatRect& objectBoundingBox, bool& objectBoundingBoxValid, RenderObject* other, FloatRect otherBoundingBox)
 {
@@ -187,11 +203,6 @@ void SVGRenderSupport::computeContainerBoundingBoxes(const RenderObject* contain
     paintInvalidationBoundingBox = strokeBoundingBox;
 }
 
-bool SVGRenderSupport::paintInfoIntersectsPaintInvalidationRect(const FloatRect& localPaintInvalidationRect, const AffineTransform& localTransform, const PaintInfo& paintInfo)
-{
-    return localTransform.mapRect(localPaintInvalidationRect).intersects(paintInfo.rect);
-}
-
 const RenderSVGRoot* SVGRenderSupport::findTreeRootObject(const RenderObject* start)
 {
     while (start && !start->isSVGRoot())