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..02f61a1d6109ed7d1ec5cf6a8b97c072019c8e2a 100644
--- a/mojo/services/view_manager/public/cpp/lib/view.cc
+++ b/mojo/services/view_manager/public/cpp/lib/view.cc
@@ -489,6 +489,17 @@ void View::LocalSetBounds(const Rect& old_bounds,
   bounds_ = new_bounds;
 }
 
+void View::LocalSetViewportMetrics(const ViewportMetrics& old_metrics,

[sky, 2015/01/27 16:35:08]

Why does this need to take old_metrics? Isn't old_metrics the same as
viewport_metrics_?

[eseidel, 2015/01/27 18:50:04]

I just tried to make it match what LocalSetBounds does. :/  I'm happy to remove
the old_metrics.

+                                   const ViewportMetrics& new_metrics) {
+  DCHECK(viewport_metrics_->size == viewport_metrics_->size);

[sky, 2015/01/27 16:35:08]

I think there is a bug where viewport_metrics_ is null for newly created views.
It can be fixed separately.

[eseidel, 2015/01/27 18:50:04]

Yes, there is.  It's fixed a little in this patch, not completely.  The trouble
when I tried to model after Bounds is that Bounds uses a mojo:Rect which because
it only contains POD types can be allocated as part of View.  Since
ViewportMetrics contains a SizePtr it can't, thus we have bugs like the null bug
you mention.

+  DCHECK(viewport_metrics_->device_pixel_ratio ==
+         viewport_metrics_->device_pixel_ratio);
+  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;