Bug 1461204 - check the residual offset for following groups. r=kats

This was missed when the residual offset was added; it's correctly checked elsewhere

MozReview-Commit-ID: 44N5vDWLBIo

--HG--
extra : rebase_source : 37b42b8df416638e84531ed088c29716e4446159

gfx/layers/wr/WebRenderCommandBuilder.cpp

@@ -948,7 +948,8 @@ Grouper::ConstructGroups(WebRenderCommandBuilder* aCommandBuilder,
       // that we're building the display list for.
       if (!groupData->mFollowingGroup.mGroupBounds.IsEqualEdges(currentGroup->mGroupBounds) ||
           groupData->mFollowingGroup.mScale != currentGroup->mScale ||
-          groupData->mFollowingGroup.mAppUnitsPerDevPixel != currentGroup->mAppUnitsPerDevPixel) {
+          groupData->mFollowingGroup.mAppUnitsPerDevPixel != currentGroup->mAppUnitsPerDevPixel ||
+          groupData->mFollowingGroup.mResidualOffset != currentGroup->mResidualOffset) {
         if (groupData->mFollowingGroup.mAppUnitsPerDevPixel != currentGroup->mAppUnitsPerDevPixel) {
           GP("app unit change following: %d %d\n", groupData->mFollowingGroup.mAppUnitsPerDevPixel, currentGroup->mAppUnitsPerDevPixel);
         }