Pass Viewport Description to compositor

Signed-off-by: Shubham Gupta <shubham13297@gmail.com>

components/compositing/compositor.rs

@@ -973,6 +973,7 @@ impl IOCompositor {
                     warn!("Sending response to get screen size failed ({error:?}).");
                 }
             },
+            CompositorMsg::Viewport(_webview_id, _viewport_description) => {},
         }
     }
 

components/compositing/tracing.rs

@@ -59,6 +59,7 @@ mod from_constellation {
                 Self::GetScreenSize(..) => target!("GetScreenSize"),
                 Self::GetAvailableScreenSize(..) => target!("GetAvailableScreenSize"),
                 Self::CollectMemoryReport(..) => target!("CollectMemoryReport"),
+                Self::Viewport(..) => target!("Viewport"),
             }
         }
     }

components/script/dom/htmlmetaelement.rs

@@ -2,6 +2,9 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+use std::str::FromStr;
+
+use compositing_traits::CompositorMsg;
 use compositing_traits::viewport_description::ViewportDescription;
 use dom_struct::dom_struct;
 use html5ever::{LocalName, Prefix, local_name, ns};
@@ -126,8 +129,19 @@ impl HTMLMetaElement {
             return;
         }
         let element = self.upcast::<Element>();
-        if let Some(content) = element.get_attribute(&ns!(), &local_name!("content")) {
-            let _viewport = ViewportDescription::from_str(&content.value()).unwrap_or_default();
+        let Some(content) = element.get_attribute(&ns!(), &local_name!("content")) else {
+            return;
+        };
+
+        if let Ok(viewport) = ViewportDescription::from_str(&content.value()) {
+            self.owner_window()
+                .compositor_api()
+                .sender()
+                .send(CompositorMsg::Viewport(
+                    self.owner_window().webview_id(),
+                    viewport,
+                ))
+                .unwrap();
         }
     }
 

components/shared/compositing/lib.rs

@@ -43,6 +43,8 @@ use webrender_api::{
     ImageKey, NativeFontHandle, PipelineId as WebRenderPipelineId,
 };
 
+use crate::viewport_description::ViewportDescription;
+
 /// Sends messages to the compositor.
 #[derive(Clone)]
 pub struct CompositorProxy {
@@ -177,6 +179,8 @@ pub enum CompositorMsg {
     /// Measure the current memory usage associated with the compositor.
     /// The report must be sent on the provided channel once it's complete.
     CollectMemoryReport(ReportsChan),
+    /// A top-level frame has parsed a viewport metatag and is sending the new constraints.
+    Viewport(WebViewId, ViewportDescription),
 }
 
 impl Debug for CompositorMsg {