Auto merge of #24677 - jdm:iframe-sizing-cleanup, r=asajeffrey

Ensure all iframes are sized correctly at creation

Following in the path of #22395, these commits serve several purposes:
* prevent layout instability early during iframe loads caused by a succession of resize events
* reduce the complexity of determining what actual DPI and initial window size values are being used at startup
* ensure that all documents have a correct initial viewport size at creation

These changes fix problems that were exposed by the changes in #24462 but are independent of that PR.

---
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] There are tests for these changes

1 files changed, 12 insertions, 1 deletions

diff --git a/components/script/dom/window.rs b/components/script/dom/window.rs
index 70099ee5866..95326b46352 100644
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@@ -89,7 +89,7 @@ use js::jsval::{JSVal, NullValue};
 use js::rust::wrappers::JS_DefineProperty;
 use js::rust::{CustomAutoRooter, CustomAutoRooterGuard, HandleValue};
 use media::WindowGLContext;
-use msg::constellation_msg::PipelineId;
+use msg::constellation_msg::{BrowsingContextId, PipelineId};
 use net_traits::image_cache::{ImageCache, ImageResponder, ImageResponse};
 use net_traits::image_cache::{PendingImageId, PendingImageResponse};
 use net_traits::storage_thread::StorageType;
@@ -1829,6 +1829,16 @@ impl Window {
         DOMString::from(resolved)
     }
 
+    pub fn inner_window_dimensions_query(
+        &self,
+        browsing_context: BrowsingContextId,
+    ) -> Option<Size2D<f32, CSSPixel>> {
+        if !self.layout_reflow(QueryMsg::InnerWindowDimensionsQuery(browsing_context)) {
+            return None;
+        }
+        self.layout_rpc.inner_window_dimensions()
+    }
+
     #[allow(unsafe_code)]
     pub fn offset_parent_query(&self, node: &Node) -> (Option<DomRoot<Element>>, UntypedRect<Au>) {
         if !self.layout_reflow(QueryMsg::OffsetParentQuery(node.to_opaque())) {
@@ -2359,6 +2369,7 @@ fn debug_reflow_events(id: PipelineId, reflow_goal: &ReflowGoal, reason: &Reflow
             &QueryMsg::StyleQuery(_n) => "\tStyleQuery",
             &QueryMsg::TextIndexQuery(..) => "\tTextIndexQuery",
             &QueryMsg::ElementInnerTextQuery(_) => "\tElementInnerTextQuery",
+            &QueryMsg::InnerWindowDimensionsQuery(_) => "\tInnerWindowDimensionsQuery",
         },
     });