Issue #2355 - Apply self-transforms to the frame of top level <svg>

We previously didn't do this because we relied on our anonymous wrapper
to perform transforms. However, that resulted in only the children
transforming, and the frame's cliprect wouldn't be updated,
giving the impression of the z-ordering being wrong.

Also adds reftests from the relevant BZ bug found later.

Resolves #2355

layout/svg/nsSVGOuterSVGFrame.cpp

@@ -721,6 +721,32 @@ nsSVGOuterSVGFrame::AttributeChanged(int32_t  aNameSpaceID,
   return NS_OK;
 }
 
+bool
+nsSVGOuterSVGFrame::IsSVGTransformed(Matrix* aOwnTransform,
+                                     Matrix* aFromParentTransform) const
+{
+  // The HasChildrenOnlyTransform() implementation of our anonymous child makes sure
+  // our transforms are applied to our children as-appropriate. So, we only care
+  // about self-transforms on our own frame, here.
+
+  bool hasTransform = false;
+
+  SVGSVGElement* content = static_cast<SVGSVGElement*>(mContent);
+  nsSVGAnimatedTransformList* animatedTransformList = content->GetAnimatedTransformList();
+  if ((animatedTransformList && animatedTransformList->HasTransform()) ||
+      content->GetAnimateMotionTransform()) {
+    if (aOwnTransform) {
+      // Apply transform
+      *aOwnTransform = gfx::ToMatrix(
+                         content->PrependLocalTransformsTo(
+                           gfxMatrix(), eUserSpaceToParent));
+    }
+    hasTransform = true;
+  }
+
+  return hasTransform;
+}
+
 //----------------------------------------------------------------------
 // painting