Add support for <iframe> elements for Layout 2020

This change adds support for the <iframe> element to Layout 2020. In
addition, certain aspects of the implementation are made the same
between both layout systems.

components/script_traits/lib.rs

@@ -82,9 +82,7 @@ pub use crate::script_msg::{
     DOMMessage, HistoryEntryReplacement, Job, JobError, JobResult, JobResultValue, JobType,
     SWManagerMsg, SWManagerSenders, ScopeThings, ServiceWorkerMsg,
 };
-pub use crate::script_msg::{
-    EventResult, IFrameSize, IFrameSizeMsg, LayoutMsg, LogEntry, ScriptMsg,
-};
+pub use crate::script_msg::{EventResult, IFrameSizeMsg, LayoutMsg, LogEntry, ScriptMsg};
 
 /// The address of a node. Layout sends these back. They must be validated via
 /// `from_untrusted_node_address` before they can be used, because we do not trust layout.

components/script_traits/script_msg.rs

@@ -41,20 +41,13 @@ use style_traits::CSSPixel;
 use webgpu::{wgpu, WebGPU, WebGPUResponseResult};
 use webrender_api::units::{DeviceIntPoint, DeviceIntSize};
 
-/// A particular iframe's size, associated with a browsing context.
-#[derive(Clone, Copy, Debug, Deserialize, Serialize)]
-pub struct IFrameSize {
-    /// The child browsing context for this iframe.
-    pub id: BrowsingContextId,
-    /// The size of the iframe.
-    pub size: Size2D<f32, CSSPixel>,
-}
-
 /// An iframe sizing operation.
 #[derive(Clone, Copy, Debug, Deserialize, Serialize)]
 pub struct IFrameSizeMsg {
-    /// The iframe sizing data.
-    pub data: IFrameSize,
+    /// The child browsing context for this iframe.
+    pub browsing_context_id: BrowsingContextId,
+    /// The size of the iframe.
+    pub size: Size2D<f32, CSSPixel>,
     /// The kind of sizing operation.
     pub type_: WindowSizeType,
 }