Plumb ViewportMetrics change notifications around the world and back.

services/view_manager/test_change_tracker.cc

Index: services/view_manager/test_change_tracker.cc
diff --git a/services/view_manager/test_change_tracker.cc b/services/view_manager/test_change_tracker.cc
index e86baf2ad39bfc986e0708c89138dfc8fab6b1d3..11b0b39e33c323f1e83407760299c8f4e9c7ab0e 100644
--- a/services/view_manager/test_change_tracker.cc
+++ b/services/view_manager/test_change_tracker.cc
@@ -49,6 +49,10 @@ std::string ChangeToDescription1(const Change& change) {
           RectToString(change.bounds).c_str(),
           RectToString(change.bounds2).c_str());
 
+    case CHANGE_TYPE_NODE_VIEWPORT_METRICS_CHANGED:
+      // TODO(sky): Not implemented.
+      return "ViewportMetricsChanged";
+
     case CHANGE_TYPE_NODE_HIERARCHY_CHANGED:
       return base::StringPrintf(
           "HierarchyChanged view=%s new_parent=%s old_parent=%s",
@@ -198,6 +202,15 @@ void TestChangeTracker::OnViewBoundsChanged(Id view_id,
   AddChange(change);
 }
 
+void TestChangeTracker::OnViewViewportMetricsChanged(
+    mojo::ViewportMetricsPtr old_metrics,
+    mojo::ViewportMetricsPtr new_metrics) {
+  Change change;
+  change.type = CHANGE_TYPE_NODE_VIEWPORT_METRICS_CHANGED;
+  // NOT IMPLEMENTED
+  AddChange(change);
+}
+
 void TestChangeTracker::OnViewHierarchyChanged(Id view_id,
                                                Id new_parent_id,
                                                Id old_parent_id,