compositor: Make PipelineDetails and pending paint metrics per-WebView (#35701)

This is one of the first big steps toward making the compositor work
per-WebView. It moves the collection of pipelines into the per-WebView
data structure in the compositor as well as the pending paint metrics.

This means that more messages need to carry information about the
WebView they apply to. Note that there are still a few places that we
need to map from `PipelineId` to `WebViewId`, so this also includes a
shared mapping which tracks this. The mapping can be removed once event
handling is fully per-WebView.

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

components/shared/webrender/lib.rs

@@ -11,7 +11,7 @@ use core::fmt;
 use std::collections::HashMap;
 use std::sync::{Arc, Mutex};
 
-use base::id::PipelineId;
+use base::id::{PipelineId, WebViewId};
 use display_list::{CompositorDisplayListInfo, ScrollTreeNodeId};
 use embedder_traits::Cursor;
 use euclid::default::Size2D as UntypedSize2D;
@@ -33,9 +33,16 @@ pub enum CrossProcessCompositorMessage {
     /// Inform WebRender of the existence of this pipeline.
     SendInitialTransaction(WebRenderPipelineId),
     /// Perform a scroll operation.
-    SendScrollNode(WebRenderPipelineId, LayoutPoint, ExternalScrollId),
+    SendScrollNode(
+        WebViewId,
+        WebRenderPipelineId,
+        LayoutPoint,
+        ExternalScrollId,
+    ),
     /// Inform WebRender of a new display list for the given pipeline.
     SendDisplayList {
+        /// The [`WebViewId`] that this display list belongs to.
+        webview_id: WebViewId,
         /// The [CompositorDisplayListInfo] that describes the display list being sent.
         display_list_info: Box<CompositorDisplayListInfo>,
         /// A descriptor of this display list used to construct this display list from raw data.
@@ -138,11 +145,13 @@ impl CrossProcessCompositorApi {
     /// Perform a scroll operation.
     pub fn send_scroll_node(
         &self,
+        webview_id: WebViewId,
         pipeline_id: WebRenderPipelineId,
         point: LayoutPoint,
         scroll_id: ExternalScrollId,
     ) {
         if let Err(e) = self.0.send(CrossProcessCompositorMessage::SendScrollNode(
+            webview_id,
             pipeline_id,
             point,
             scroll_id,
@@ -154,12 +163,14 @@ impl CrossProcessCompositorApi {
     /// Inform WebRender of a new display list for the given pipeline.
     pub fn send_display_list(
         &self,
+        webview_id: WebViewId,
         display_list_info: CompositorDisplayListInfo,
         list: BuiltDisplayList,
     ) {
         let (display_list_data, display_list_descriptor) = list.into_data();
         let (display_list_sender, display_list_receiver) = ipc::bytes_channel().unwrap();
         if let Err(e) = self.0.send(CrossProcessCompositorMessage::SendDisplayList {
+            webview_id,
             display_list_info: Box::new(display_list_info),
             display_list_descriptor,
             display_list_receiver,