Disable antialiasing of borders again, for Linux only, to avoid the performance penalty of pushing/popping groups. b=380473 r=vlad

layout/base/nsCSSRendering.cpp

@@ -2304,6 +2304,17 @@ nsCSSRendering::PaintBorder(nsPresContext* aPresContext,
     ctx->SetMatrix(mat);
   }
 
+#ifdef MOZ_WIDGET_GTK2
+// Temporarily disable antialising of borders until the performance
+// is acceptable.
+#define DISABLE_BORDER_ANTIALIAS
+#endif
+
+#ifdef DISABLE_BORDER_ANTIALIAS /* XXX temporary */
+  gfxContext::AntialiasMode oldMode = ctx->CurrentAntialiasMode();
+  ctx->SetAntialiasMode(gfxContext::MODE_ALIASED);
+#endif
+
   // if we're going to do separate sides, we need to do it as
   // a temporary surface group
   if (doSeparateSides) {
@@ -2324,10 +2335,12 @@ nsCSSRendering::PaintBorder(nsPresContext* aPresContext,
       ctx->Clip();
     }
 
+#ifndef DISABLE_BORDER_ANTIALIAS
     // start a compositing group and render using ADD so that
     // we get correct behaviour at the joins
     ctx->PushGroup(gfxASurface::CONTENT_COLOR_ALPHA);
     ctx->SetOperator(gfxContext::OPERATOR_ADD);
+#endif
   } else if (aGap) {
     gfxRect gapRect(gfxFloat(aGap->x) / twipsPerPixel,
                     gfxFloat(aGap->y) / twipsPerPixel,
@@ -2417,10 +2430,17 @@ nsCSSRendering::PaintBorder(nsPresContext* aPresContext,
       ctx->Restore();
   }
 
+#ifndef DISABLE_BORDER_ANTIALIAS
   if (doSeparateSides) {
     ctx->PopGroupToSource();
     ctx->Paint();
   }
+#endif
+
+#ifdef DISABLE_BORDER_ANTIALIAS /* XXX temporary */
+  // Does |Restore| below restore this?
+  ctx->SetAntialiasMode(oldMode);
+#endif
 
   ctx->Restore();