diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index a056a194dbb1a0..66ac13c8331800 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -28,6 +28,7 @@
 #include "base/timer/elapsed_timer.h"
 #include "base/trace_event/trace_event.h"
 #include "base/trace_event/trace_event_argument.h"
+#include "build/build_config.h"
 #include "cc/base/devtools_instrumentation.h"
 #include "cc/base/histograms.h"
 #include "cc/base/math_util.h"
@@ -1079,7 +1080,11 @@ void LayerTreeHost::SetViewportSizeAndScale(
   if (changed) {
     SetPropertyTreesNeedRebuild();
     SetNeedsCommit();
+#if defined(OS_MACOSX)
+    // TODO(ccameron): This check is not valid on Aura or Mus yet, but should
+    // be.
     CHECK(!has_pushed_local_surface_id_ || !local_surface_id_.is_valid());
+#endif
   }
 }
 
diff --git a/testing/buildbot/filters/mash.ash_unittests.filter b/testing/buildbot/filters/mash.ash_unittests.filter
index 21635d488a002c..ea63b831a9ac3f 100644
--- a/testing/buildbot/filters/mash.ash_unittests.filter
+++ b/testing/buildbot/filters/mash.ash_unittests.filter
@@ -89,8 +89,6 @@
 -HighlighterControllerTest.HighlighterGesturesScaled
 # Test is flaky. http://crbug.com/817327.
 -HighlighterControllerTest.HighlighterGesturesRotated
-# Test fails due to DSF routing bug https://crbug.com/821535
--HighlighterControllerTest.SelectionInsideScreen
 
 # TODO: Top-of-screen mouse reveal doesn't work, maybe problem with
 # EventGenerator. http://crbug.com/698085