cc: Fix bug where tabs have the wrong scale factor

cc/trees/layer_tree_impl_unittest.cc

Index: cc/trees/layer_tree_impl_unittest.cc
diff --git a/cc/trees/layer_tree_impl_unittest.cc b/cc/trees/layer_tree_impl_unittest.cc
index 5298ed9c4103585e422a7a4d9eb689e379382e97..393266e9d7f3be9a32160b7fc3852c9147aa71da 100644
--- a/cc/trees/layer_tree_impl_unittest.cc
+++ b/cc/trees/layer_tree_impl_unittest.cc
@@ -2370,5 +2370,13 @@ TEST_F(LayerTreeImplTest, NumLayersSmallTree) {
   EXPECT_EQ(4u, host_impl().active_tree()->NumLayers());
 }
 
+TEST_F(LayerTreeImplTest, DeviceScaleFactorNeedsDrawPropertiesUpdate) {
+  host_impl().active_tree()->SetDeviceScaleFactor(1.f);
+  host_impl().active_tree()->UpdateDrawProperties(false);
+  EXPECT_FALSE(host_impl().active_tree()->needs_update_draw_properties());
+  host_impl().active_tree()->SetDeviceScaleFactor(2.f);
+  EXPECT_TRUE(host_impl().active_tree()->needs_update_draw_properties());
+}
+
 }  // namespace
 }  // namespace cc