Bug 1756197. Avoid clipping if we're just going to fill the path. r=g…

…fx-reviewers,nical

This avoids having to rasterize the path twice. Once for the clip path and once for
the fill. It will also give us correct antialiasing on the edges.

Differential Revision: https://phabricator.services.mozilla.com/D139137

layout/svg/SVGIntegrationUtils.cpp

@@ -758,16 +758,19 @@ bool SVGIntegrationUtils::PaintMask(const PaintFramesParams& aParams,
     MoveContextOriginToUserSpace(firstFrame, aParams);
 
     basicShapeSR.SetContext(&ctx);
-    CSSClipPathInstance::ApplyBasicShapeOrPathClip(
-        ctx, frame, SVGUtils::GetCSSPxToDevPxMatrix(frame));
+    gfxMatrix mat = SVGUtils::GetCSSPxToDevPxMatrix(frame);
     if (!maskUsage.shouldGenerateMaskLayer) {
       // Only have basic-shape clip-path effect. Fill clipped region by
       // opaque white.
       ctx.SetDeviceColor(DeviceColor::MaskOpaqueWhite());
+      RefPtr<Path> path = CSSClipPathInstance::CreateClipPathForFrame(
+          ctx.GetDrawTarget(), frame, mat);
+      ctx.SetPath(path);
       ctx.Fill();
 
       return true;
     }
+    CSSClipPathInstance::ApplyBasicShapeOrPathClip(ctx, frame, mat);
   }
 
   // Paint mask onto ctx.