Clear absolute clip rects when transform changes

Source/core/rendering/RenderLayer.cpp

Index: Source/core/rendering/RenderLayer.cpp
diff --git a/Source/core/rendering/RenderLayer.cpp b/Source/core/rendering/RenderLayer.cpp
index 041337f6fd6b25e64b4d608d8c43317525dc7f92..748bcf16cd4d33f5bc0fed461f17d82041d6e332 100644
--- a/Source/core/rendering/RenderLayer.cpp
+++ b/Source/core/rendering/RenderLayer.cpp
@@ -504,6 +504,8 @@ void RenderLayer::updateTransform()
 
         // Layers with transforms act as clip rects roots, so clear the cached clip rects here.
         m_clipper.clearClipRectsIncludingDescendants();
+    } else if (hasTransform) {
+        m_clipper.clearClipRectsIncludingDescendants(AbsoluteClipRects);

[Ian Vollick, 2014/06/17 15:57:28]

Doesn't this mean that even if we call updateTransform, and the transform
doesn't change, we'll always clear our AbsoluteClipRects? Should we compare the
old and new transforms?

[ajuma, 2014/06/17 16:01:50]

The caller of updateTransform (RenderLayer::styleChanged) already checks if the
old and new transforms are the same, and only calls updateTransform when they're
not.

[Ian Vollick, 2014/06/17 16:07:25]

Ah, thanks. In that case, maybe we could add an ASSERT here just to make sure
that remains true.

[ajuma, 2014/06/17 17:10:40]

Adding an ASSERT is a good idea, but we don't have access to the old style here,
just the new one. We also can't compare m_transform before and after the
applyTransform below since the transform (expressed as TransformOperations)
could change without changing the resulting matrix (also, having to copy the old
m_transform just for the sake of an ASSERT doesn't seem great).

     }
 
     if (hasTransform) {