Plumb ViewportMetrics change notifications around the world and back.

services/view_manager/server_view_delegate.h

Index: services/view_manager/server_view_delegate.h
diff --git a/services/view_manager/server_view_delegate.h b/services/view_manager/server_view_delegate.h
index 9a9d5907fd5fa5f8903ccd43f83bf2289802fd46..915d8a2f45e6c78f2ef602fcdda141515e8f1711 100644
--- a/services/view_manager/server_view_delegate.h
+++ b/services/view_manager/server_view_delegate.h
@@ -11,6 +11,10 @@ namespace gfx {
 class Rect;
 }
 
+namespace mojo {
+class ViewportMetrics;
+}
+
 namespace view_manager {
 
 class ServerView;
@@ -37,6 +41,11 @@ class ServerViewDelegate {
                                    const gfx::Rect& old_bounds,
                                    const gfx::Rect& new_bounds) = 0;
 
+  virtual void OnViewViewportMetricsChanged(
+      const ServerView* view,
+      const mojo::ViewportMetrics& old_metrics,
+      const mojo::ViewportMetrics& new_metrics) = 0;
+
   virtual void OnViewSurfaceIdChanged(const ServerView* view) = 0;
 
   virtual void OnViewReordered(const ServerView* view,