Plumb ViewportMetrics change notifications around the world and back.

mojo/services/view_manager/public/cpp/lib/view.cc

Index: mojo/services/view_manager/public/cpp/lib/view.cc
diff --git a/mojo/services/view_manager/public/cpp/lib/view.cc b/mojo/services/view_manager/public/cpp/lib/view.cc
index c07edebd2f9e05a8ba746d76124043126b2995de..f7e77844ce9cfbd191051b8594da239aa3b71cce 100644
--- a/mojo/services/view_manager/public/cpp/lib/view.cc
+++ b/mojo/services/view_manager/public/cpp/lib/view.cc
@@ -382,10 +382,20 @@ void View::Embed(const String& url,
 ////////////////////////////////////////////////////////////////////////////////
 // View, protected:
 
+namespace {
+
+ViewportMetricsPtr CreateEmptyViewportMetrics() {
+  ViewportMetricsPtr metrics = ViewportMetrics::New();
+  metrics->size = Size::New();
+  return metrics;
+}
+}
+
 View::View()
     : manager_(NULL),
       id_(static_cast<Id>(-1)),
       parent_(NULL),
+      viewport_metrics_(CreateEmptyViewportMetrics()),
       visible_(true),
       drawn_(false) {
 }
@@ -425,6 +435,7 @@ View::View(ViewManager* manager, Id id)
     : manager_(manager),
       id_(id),
       parent_(nullptr),
+      viewport_metrics_(CreateEmptyViewportMetrics()),
       visible_(false),
       drawn_(false) {
 }
@@ -489,6 +500,15 @@ void View::LocalSetBounds(const Rect& old_bounds,
   bounds_ = new_bounds;
 }
 
+void View::LocalSetViewportMetrics(const ViewportMetrics& old_metrics,
+                                   const ViewportMetrics& new_metrics) {
+  // TODO(eseidel): We could check old_metrics against viewport_metrics_.
+  viewport_metrics_ = new_metrics.Clone();
+  FOR_EACH_OBSERVER(
+      ViewObserver, observers_,
+      OnViewViewportMetricsChanged(this, old_metrics, new_metrics));
+}
+
 void View::LocalSetDrawn(bool value) {
   if (drawn_ == value)
     return;