--- a/layout/svg/nsSVGFilterInstance.cpp
+++ b/layout/svg/nsSVGFilterInstance.cpp
@@ -51,74 +51,19 @@ nsSVGFilterInstance::nsSVGFilterInstance
   if (!mFilterElement) {
     NS_NOTREACHED("filter frame should have a related element");
     return;
   }
 
   mPrimitiveUnits =
     mFilterFrame->GetEnumValue(SVGFilterElement::PRIMITIVEUNITS);
 
-  nsresult rv = ComputeBounds();
-  if (NS_FAILED(rv)) {
-    return;
-  }
-
   mInitialized = true;
 }
 
-nsresult
-nsSVGFilterInstance::ComputeBounds()
-{
-  // XXX if filterUnits is set (or has defaulted) to objectBoundingBox, we
-  // should send a warning to the error console if the author has used lengths
-  // with units. This is a common mistake and can result in the filter region
-  // being *massive* below (because we ignore the units and interpret the number
-  // as a factor of the bbox width/height). We should also send a warning if the
-  // user uses a number without units (a future SVG spec should really
-  // deprecate that, since it's too confusing for a bare number to be sometimes
-  // interpreted as a fraction of the bounding box and sometimes as user-space
-  // units). So really only percentage values should be used in this case.
-
-  // Set the user space bounds (i.e. the filter region in user space).
-  nsSVGLength2 XYWH[4];
-  static_assert(sizeof(mFilterElement->mLengthAttributes) == sizeof(XYWH),
-                "XYWH size incorrect");
-  memcpy(XYWH, mFilterElement->mLengthAttributes,
-    sizeof(mFilterElement->mLengthAttributes));
-  XYWH[0] = *mFilterFrame->GetLengthValue(SVGFilterElement::ATTR_X);
-  XYWH[1] = *mFilterFrame->GetLengthValue(SVGFilterElement::ATTR_Y);
-  XYWH[2] = *mFilterFrame->GetLengthValue(SVGFilterElement::ATTR_WIDTH);
-  XYWH[3] = *mFilterFrame->GetLengthValue(SVGFilterElement::ATTR_HEIGHT);
-  uint16_t filterUnits =
-    mFilterFrame->GetEnumValue(SVGFilterElement::FILTERUNITS);
-  gfxRect userSpaceBounds = nsSVGUtils::GetRelativeRect(filterUnits,
-    XYWH, mTargetBBox, mMetrics);
-
-  // Transform the user space bounds to filter space, so we
-  // can align them with the pixel boundries of the offscreen surface.
-  // The offscreen surface has the same scale as filter space.
-  gfxRect filterSpaceBounds = UserSpaceToFilterSpace(userSpaceBounds);
-  filterSpaceBounds.RoundOut();
-  if (filterSpaceBounds.width <= 0 || filterSpaceBounds.height <= 0) {
-    // 0 disables rendering, < 0 is error. dispatch error console warning
-    // or error as appropriate.
-    return NS_ERROR_FAILURE;
-  }
-
-  // Set the filter space bounds.
-  if (!gfxUtils::GfxRectToIntRect(filterSpaceBounds, &mFilterSpaceBounds)) {
-    // The filter region is way too big if there is float -> int overflow.
-    return NS_ERROR_FAILURE;
-  }
-
-  mUserSpaceBounds = FilterSpaceToUserSpace(filterSpaceBounds);
-
-  return NS_OK;
-}
-
 nsSVGFilterFrame*
 nsSVGFilterInstance::GetFilterFrame(nsIFrame* aTargetFrame)
 {
   if (mFilter.GetType() != NS_STYLE_FILTER_URL) {
     // The filter is not an SVG reference filter.
     return nullptr;
   }
 

--- a/layout/svg/nsSVGFilterInstance.h
+++ b/layout/svg/nsSVGFilterInstance.h
@@ -106,24 +106,16 @@ public:
    * element in aPrimitiveDescrs, or the SourceGraphic input if this is the first
    * filter in the filter chain.
    */
   nsresult BuildPrimitives(nsTArray<FilterPrimitiveDescription>& aPrimitiveDescrs,
                            nsTArray<RefPtr<SourceSurface>>& aInputImages,
                            bool aInputIsTainted);
 
   /**
-   * Returns the user specified "filter region", in the filtered element's user
-   * space, after it has been adjusted out (if necessary) so that its edges
-   * coincide with pixel boundaries of the offscreen surface into which the
-   * filtered output would/will be painted.
-   */
-  gfxRect GetFilterRegion() const { return mUserSpaceBounds; }
-
-  /**
    * Returns the size of the user specified "filter region", in filter space.
    */
   nsIntRect GetFilterSpaceBounds() const { return mFilterSpaceBounds; }
 
   float GetPrimitiveNumber(uint8_t aCtxType, const nsSVGNumber2 *aNumber) const
   {
     return GetPrimitiveNumber(aCtxType, aNumber->GetAnimValue());
   }
@@ -203,22 +195,16 @@ private:
    * FilterPrimitiveDescription representing "another-primitive".
    */
   nsresult GetSourceIndices(nsSVGFE* aPrimitiveElement,
                             nsTArray<FilterPrimitiveDescription>& aPrimitiveDescrs,
                             const nsDataHashtable<nsStringHashKey, int32_t>& aImageTable,
                             nsTArray<int32_t>& aSourceIndices);
 
   /**
-   * Compute the filter region in user space, filter space, and filter
-   * space.
-   */
-  nsresult ComputeBounds();
-
-  /**
    * The SVG reference filter originally from the style system.
    */
   const nsStyleFilter& mFilter;
 
   /**
    * The filtered element.
    */
   nsIContent* mTargetContent;
@@ -241,17 +227,16 @@ private:
   /**
    * The SVG bbox of the element that is being filtered, in user space.
    */
   gfxRect mTargetBBox;
 
   /**
    * The "filter region" in various spaces.
    */
-  gfxRect mUserSpaceBounds;
   nsIntRect mFilterSpaceBounds;
 
   /**
    * The scale factors between user space and filter space.
    */
   gfxSize mUserSpaceToFilterSpaceScale;
   gfxSize mFilterSpaceToUserSpaceScale;