Plumb ViewportMetrics change notifications around the world and back.

services/view_manager/view_manager_service_unittest.cc

Index: services/view_manager/view_manager_service_unittest.cc
diff --git a/services/view_manager/view_manager_service_unittest.cc b/services/view_manager/view_manager_service_unittest.cc
index e1e88930ffdc51242f8718bbd8beab6b67c147fe..9c07771efc6866b2135e89d846d333d26e130b98 100644
--- a/services/view_manager/view_manager_service_unittest.cc
+++ b/services/view_manager/view_manager_service_unittest.cc
@@ -64,6 +64,13 @@ class TestViewManagerClient : public mojo::ViewManagerClient {
                            mojo::RectPtr new_bounds) override {
     tracker_.OnViewBoundsChanged(view, old_bounds.Pass(), new_bounds.Pass());
   }
+  void OnViewViewportMetricsChanged(
+      uint32_t view,
+      mojo::ViewportMetricsPtr old_metrics,
+      mojo::ViewportMetricsPtr new_metrics) override {
+    tracker_.OnViewViewportMetricsChanged(view, old_metrics.Pass(),
+                                          new_metrics.Pass());
+  }
   void OnViewHierarchyChanged(uint32_t view,
                               uint32_t new_parent,
                               uint32_t old_parent,