script: Pass more information to the MouseEvent constructor (#37672)

- Instead of eagerly computing `pageX` and `pageY`, collect the offset
  from the content's initial containing block in the compositor and pass
  that information through to `MouseEvent`. This prevents a layout flush
  that was happening when eagerly trying to fetch `Document` scroll
  offsets.
- Pass keyboard modifiers properly to `MouseEvent`.
- Now all this information is stored and passed as `Point2D` (typed) and
  `Modifiers` which greatly reduces the amount of arguments that need to
  be passed around.

Testing: It is difficult to test input events as they require WebDriver
which
isn't completely working yet. I have manually run Speedometer 2.1 and I
have
verified that this fixes the regression from #37601.
Fixes: #37601.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

components/script/dom/node.rs

@@ -18,11 +18,13 @@ use bitflags::bitflags;
 use devtools_traits::NodeInfo;
 use dom_struct::dom_struct;
 use embedder_traits::UntrustedNodeAddress;
+use euclid::Point2D;
 use euclid::default::{Rect, Size2D};
 use html5ever::serialize::HtmlSerializer;
 use html5ever::{Namespace, Prefix, QualName, ns, serialize as html_serialize};
 use js::jsapi::JSObject;
 use js::rust::HandleObject;
+use keyboard_types::Modifiers;
 use layout_api::{
     GenericLayoutData, HTMLCanvasData, HTMLMediaData, LayoutElementType, LayoutNodeType, QueryMsg,
     SVGSVGData, StyleData, TrustedNodeAddress,
@@ -479,14 +481,10 @@ impl Node {
             EventCancelable::Cancelable,        // Step 3: cancelable
             Some(&window),                      // Step 7: view
             0,                                  // detail uninitialized
-            0,                                  // coordinates uninitialized
-            0,                                  // coordinates uninitialized
-            0,                                  // coordinates uninitialized
-            0,                                  // coordinates uninitialized
-            false,                              // ctrl_key
-            false,                              // alt_key
-            false,                              // shift_key
-            false,                              // meta_key
+            Point2D::zero(),                    // coordinates uninitialized
+            Point2D::zero(),                    // coordinates uninitialized
+            Point2D::zero(),                    // coordinates uninitialized
+            Modifiers::empty(),                 // empty modifiers
             0,                                  // button, left mouse button
             0,                                  // buttons
             None,                               // related_target