Bug 1458993 - Use correct bounds for WR solid color. r=miko

MozReview-Commit-ID: Gp5C4v8qJXI

Differential Revision: https://phabricator.services.mozilla.com/D12713

--HG--
extra : moz-landing-system : lando

layout/painting/nsDisplayList.cpp

@@ -3581,7 +3581,7 @@ nsDisplaySolidColor::CreateWebRenderCommands(
   nsDisplayListBuilder* aDisplayListBuilder)
 {
   LayoutDeviceRect bounds = LayoutDeviceRect::FromAppUnits(
-    GetPaintRect(), mFrame->PresContext()->AppUnitsPerDevPixel());
+    mBounds, mFrame->PresContext()->AppUnitsPerDevPixel());
   wr::LayoutRect roundedRect = wr::ToRoundedLayoutRect(bounds);
 
   aBuilder.PushRect(roundedRect,