dom: Calculate the viewport size of iframes when they are first added to the tree.

components/script/dom/htmliframeelement.rs

@@ -28,7 +28,6 @@ use crate::dom::windowproxy::WindowProxy;
 use crate::script_thread::ScriptThread;
 use crate::task_source::TaskSource;
 use dom_struct::dom_struct;
-use euclid::Size2D;
 use html5ever::{LocalName, Prefix};
 use ipc_channel::ipc;
 use msg::constellation_msg::{BrowsingContextId, PipelineId, TopLevelBrowsingContextId};
@@ -173,6 +172,13 @@ impl HTMLIFrameElement {
             replace: replace,
         };
 
+        let window_size = WindowSizeData {
+            initial_viewport: window
+                .inner_window_dimensions_query(browsing_context_id)
+                .unwrap_or_default(),
+            device_pixel_ratio: window.device_pixel_ratio(),
+        };
+
         match nav_type {
             NavigationType::InitialAboutBlank => {
                 let (pipeline_sender, pipeline_receiver) = ipc::channel().unwrap();
@@ -198,13 +204,7 @@ impl HTMLIFrameElement {
                     opener: None,
                     load_data: load_data,
                     pipeline_port: pipeline_receiver,
-                    window_size: WindowSizeData {
-                        initial_viewport: {
-                            let rect = self.upcast::<Node>().bounding_content_box_or_zero();
-                            Size2D::new(rect.size.width.to_f32_px(), rect.size.height.to_f32_px())
-                        },
-                        device_pixel_ratio: window.device_pixel_ratio(),
-                    },
+                    window_size,
                 };
 
                 self.pipeline_id.set(Some(new_pipeline_id));