Refactor SetViewportLayerIds to use a struct instead of 6 values

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 756a33bb0af2a1df39bcb8e2c55f43f990c46a99..836ba53011832173e6ca35d22e962dee2b0f88fc 100644
--- a/cc/trees/layer_tree_impl_unittest.cc
+++ b/cc/trees/layer_tree_impl_unittest.cc
@@ -1439,9 +1439,10 @@ TEST_F(LayerTreeImplTest,
   host_impl().SetViewportSize(scaled_bounds_for_root);
 
   host_impl().active_tree()->SetDeviceScaleFactor(device_scale_factor);
-  host_impl().active_tree()->SetViewportLayersFromIds(
-      Layer::INVALID_ID, 1, Layer::INVALID_ID, Layer::INVALID_ID, 1,
-      Layer::INVALID_ID);
+  LayerTreeImpl::ViewportLayerIds viewport_ids;
+  viewport_ids.page_scale = 1;
+  viewport_ids.inner_viewport_scroll = 1;
+  host_impl().active_tree()->SetViewportLayersFromIds(viewport_ids);
   host_impl().active_tree()->BuildLayerListAndPropertyTreesForTesting();
   host_impl().active_tree()->PushPageScaleFromMainThread(
       page_scale_factor, page_scale_factor, max_page_scale_factor);
@@ -1667,9 +1668,10 @@ TEST_F(LayerTreeImplTest,
   host_impl().SetViewportSize(scaled_bounds_for_root);
 
   host_impl().active_tree()->SetDeviceScaleFactor(device_scale_factor);
-  host_impl().active_tree()->SetViewportLayersFromIds(
-      Layer::INVALID_ID, 1, Layer::INVALID_ID, Layer::INVALID_ID, 1,
-      Layer::INVALID_ID);
+  LayerTreeImpl::ViewportLayerIds viewport_ids;
+  viewport_ids.page_scale = 1;
+  viewport_ids.inner_viewport_scroll = 1;
+  host_impl().active_tree()->SetViewportLayersFromIds(viewport_ids);
   host_impl().active_tree()->BuildLayerListAndPropertyTreesForTesting();
   host_impl().active_tree()->PushPageScaleFromMainThread(
       page_scale_factor, page_scale_factor, max_page_scale_factor);
@@ -2060,9 +2062,9 @@ TEST_F(LayerTreeImplTest, SelectionBoundsForScaledLayers) {
       root->bounds(), device_scale_factor * page_scale_factor);
   host_impl().SetViewportSize(scaled_bounds_for_root);
 
-  host_impl().active_tree()->SetViewportLayersFromIds(
-      Layer::INVALID_ID, root->id(), Layer::INVALID_ID, Layer::INVALID_ID,
-      Layer::INVALID_ID, Layer::INVALID_ID);
+  LayerTreeImpl::ViewportLayerIds viewport_ids;
+  viewport_ids.page_scale = root->id();
+  host_impl().active_tree()->SetViewportLayersFromIds(viewport_ids);
   host_impl().active_tree()->SetDeviceScaleFactor(device_scale_factor);
   host_impl().active_tree()->SetPageScaleOnActiveTree(page_scale_factor);