Auto merge of #23988 - georgeroman:implement_pointer_up_and_down_actions, r=jdm

Implement pointerDown and pointerUp webdriver actions

<!-- Please describe your changes on the following line: -->

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `___` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors

<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/23988)
<!-- Reviewable:end -->

components/constellation/constellation.rs

@@ -3490,6 +3490,15 @@ where
                     return self.handle_send_error(pipeline_id, e);
                 }
             },
+            WebDriverCommandMsg::MouseButtonAction(mouse_event_type, mouse_button, x, y) => {
+                self.compositor_proxy
+                    .send(ToCompositorMsg::WebDriverMouseButtonEvent(
+                        mouse_event_type,
+                        mouse_button,
+                        x,
+                        y,
+                    ));
+            },
             WebDriverCommandMsg::TakeScreenshot(_, reply) => {
                 self.compositor_proxy
                     .send(ToCompositorMsg::CreatePng(reply));