Stricter layout checks in LayoutSVGResourceClipper/Masker

We should no longer call the ResourceBoundingBox() method on the above
classes during layout, so make the checking stricter by removing the
SelfNeedsLayout() check and adding a DCHECK on NeedsLayout().

Bug: 1028061
Change-Id: I00f406e760f5a15a70575e24f6232da4389b7f92
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2466240Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#816252}

third_party/blink/renderer/core/layout/svg/layout_svg_resource_clipper.cc

@@ -270,9 +270,7 @@ bool LayoutSVGResourceClipper::HitTestClipContent(
 FloatRect LayoutSVGResourceClipper::ResourceBoundingBox(
     const FloatRect& reference_box) {
   NOT_DESTROYED();
-  // The resource has not been layouted yet. Return the reference box.
-  if (SelfNeedsLayout())
-    return reference_box;
+  DCHECK(!NeedsLayout());
 
   if (local_clip_bounds_.IsEmpty())
     CalculateLocalClipBounds();

third_party/blink/renderer/core/layout/svg/layout_svg_resource_masker.cc

@@ -105,6 +105,7 @@ FloatRect LayoutSVGResourceMasker::ResourceBoundingBox(
     const FloatRect& reference_box,
     float reference_box_zoom) {
   NOT_DESTROYED();
+  DCHECK(!NeedsLayout());
   auto* mask_element = To<SVGMaskElement>(GetElement());
   DCHECK(mask_element);
 
@@ -117,10 +118,6 @@ FloatRect LayoutSVGResourceMasker::ResourceBoundingBox(
   if (mask_units == SVGUnitTypes::kSvgUnitTypeUserspaceonuse)
     mask_boundaries.Scale(reference_box_zoom);
 
-  // Resource was not layouted yet. Give back clipping rect of the mask.
-  if (SelfNeedsLayout())
-    return mask_boundaries;
-
   if (mask_content_boundaries_.IsEmpty())
     CalculateMaskContentVisualRect();