Initial internal support for multiple webviews (#31417)

* Add multiple concurrent top-level browsing contexts

Co-authored-by: Delan Azabani <dazabani@igalia.com>

* Rename variables and comments

There are some variable and comments still use browser as names.
This commit renames them to webview.

* Update log message from web view to webview

* Revert offscreen_framebuffer_id rename

* Rename all web view to webview

* Cargo fmt

* Fix viewport/event/clear coordinates when multiview is disabled

* Only deprecate things when multiview is enabled

* Update WebViewManger with shown and invisible sets

Replace visible_webviews and native_window_is_visible with shown_webviews
and invisible_webviews. Add 4 more methods to set them accordingly. The
behavior of is_effectively_visible will return true if the wbview is in
shown_webviews set but not in invisible_webviews.

* Update variant behaviors

* Rename WebViewVisibilityChanged to MarkWebViewInvisible

* Fix unit test by marking id 3 visible again

* Update MarkWebViewInvisible and add UnmarkWebViewInvisible

* Update format and doc comments

* Clean up doc comments

* Address style and naming changes

* Rename UpdateWebView to UpdateFrameTreeForWebView

* constellation: send frame tree unconditionally over focus and feature

* Clarify shown and invisible sets in constellation WebViewManager

* Eliminate forward_to_constellation!()

* Actually remove the unused macro

* Don’t gate compositor changes on multiview feature flag

* Update todo in mouse event dispatch

* Pass all visible webview ids in a single ReadyToPresent message

* Fix compile and lint errors

* servoshell: fix gap between minibrowser toolbar and webview

* Fix failure in /_mozilla/mozilla/window_resizeTo.html

* Fix compile warnings

* Remove stray dbg!()

* Remove confusing “effectively visible” logic (see #31815, #31816)

* Allow embedder to show/hide/raise webviews without ipc

* Update root pipeline only when painting order actually changes

* Stop gating old focus and SetFrameTree behaviour behind Cargo feature

* Use webview_id and WebViewId in webview-related code

* Improve logging of webview-related embedder events

* Allow webview Show and Raise events to optionally hide all others

* Don’t do anything in response to WebViewPaintingOrder

* Remove WebViewPaintingOrder, since its payload is unreliable

* On MoveResizeWebView, only update root pipeline if rect changed

* Rename IOCompositor methods for clarity

* compositor: add event tracing; log webview ops even without ipc

* Add temporary debug logging

* Add more temporary debug logging

* Remove temporary logging in compositor

* Remove temporary debug logging

* Add temporary debug logging, but defer I/O until panic

* Capture a backtrace with each crash log entry

* Proper error handling without panicking in WebViewManager

* Clean up imports in constellation

---------

Co-authored-by: Delan Azabani <dazabani@igalia.com>
Co-authored-by: Martin Robinson <mrobinson@igalia.com>

components/shared/embedder/lib.rs

@@ -10,7 +10,7 @@ use crossbeam_channel::{Receiver, Sender};
 use ipc_channel::ipc::IpcSender;
 use keyboard_types::KeyboardEvent;
 use log::warn;
-use msg::constellation_msg::{InputMethodType, PipelineId, TopLevelBrowsingContextId};
+use msg::constellation_msg::{InputMethodType, PipelineId, TopLevelBrowsingContextId, WebViewId};
 use num_derive::FromPrimitive;
 use serde::{Deserialize, Serialize};
 use servo_url::ServoUrl;
@@ -156,13 +156,13 @@ pub enum EmbedderMsg {
     AllowNavigationRequest(PipelineId, ServoUrl),
     /// Whether or not to allow script to open a new tab/browser
     AllowOpeningWebView(IpcSender<bool>),
-    /// A browser was created
+    /// A webview was created.
     WebViewOpened(TopLevelBrowsingContextId),
-    /// A browser was destroyed
+    /// A webview was destroyed.
     WebViewClosed(TopLevelBrowsingContextId),
-    /// A browser gained focus for keyboard events
+    /// A webview gained focus for keyboard events.
     WebViewFocused(TopLevelBrowsingContextId),
-    /// All browsers lost focus for keyboard events
+    /// All webviews lost focus for keyboard events.
     WebViewBlurred,
     /// Wether or not to unload a document
     AllowUnload(IpcSender<bool>),
@@ -210,8 +210,8 @@ pub enum EmbedderMsg {
     MediaSessionEvent(MediaSessionEvent),
     /// Report the status of Devtools Server with a token that can be used to bypass the permission prompt.
     OnDevtoolsStarted(Result<u16, ()>, String),
-    /// Compositing done, but external code needs to present.
-    ReadyToPresent,
+    /// Notify the embedder that it needs to present a new frame.
+    ReadyToPresent(Vec<WebViewId>),
     /// The given event was delivered to a pipeline in the given browser.
     EventDelivered(CompositorEventVariant),
 }
@@ -261,12 +261,12 @@ impl Debug for EmbedderMsg {
             EmbedderMsg::WebViewOpened(..) => write!(f, "WebViewOpened"),
             EmbedderMsg::WebViewClosed(..) => write!(f, "WebViewClosed"),
             EmbedderMsg::WebViewFocused(..) => write!(f, "WebViewFocused"),
-            EmbedderMsg::WebViewBlurred => write!(f, "WebViewUnfocused"),
+            EmbedderMsg::WebViewBlurred => write!(f, "WebViewBlurred"),
             EmbedderMsg::ReportProfile(..) => write!(f, "ReportProfile"),
             EmbedderMsg::MediaSessionEvent(..) => write!(f, "MediaSessionEvent"),
             EmbedderMsg::OnDevtoolsStarted(..) => write!(f, "OnDevtoolsStarted"),
             EmbedderMsg::ShowContextMenu(..) => write!(f, "ShowContextMenu"),
-            EmbedderMsg::ReadyToPresent => write!(f, "ReadyToPresent"),
+            EmbedderMsg::ReadyToPresent(..) => write!(f, "ReadyToPresent"),
             EmbedderMsg::EventDelivered(..) => write!(f, "HitTestedEvent"),
         }
     }