3 files changed, 34 insertions, 8 deletions
diff --git a/components/shared/compositing/lib.rs b/components/shared/compositing/lib.rs
index 8dadf93d628..c2acb83f240 100644
--- a/components/shared/compositing/lib.rs
+++ b/components/shared/compositing/lib.rs
@@ -111,12 +111,12 @@ pub enum CompositorMsg {
         MouseButton,
         f32,
         f32,
-        WebDriverMessageId,
+        Option<WebDriverMessageId>,
     ),
     /// WebDriver mouse move event
-    WebDriverMouseMoveEvent(WebViewId, f32, f32, WebDriverMessageId),
+    WebDriverMouseMoveEvent(WebViewId, f32, f32, Option<WebDriverMessageId>),
     // Webdriver wheel scroll event
-    WebDriverWheelScrollEvent(WebViewId, f32, f32, f64, f64),
+    WebDriverWheelScrollEvent(WebViewId, f32, f32, f64, f64, Option<WebDriverMessageId>),
 
     /// Inform WebRender of the existence of this pipeline.
     SendInitialTransaction(WebRenderPipelineId),
diff --git a/components/shared/embedder/input_events.rs b/components/shared/embedder/input_events.rs
index ff48bd7b7d8..d5c0c7bc46a 100644
--- a/components/shared/embedder/input_events.rs
+++ b/components/shared/embedder/input_events.rs
@@ -54,7 +54,7 @@ impl InputEvent {
             InputEvent::MouseButton(event) => event.webdriver_id,
             InputEvent::MouseMove(event) => event.webdriver_id,
             InputEvent::Touch(..) => None,
-            InputEvent::Wheel(..) => None,
+            InputEvent::Wheel(event) => event.webdriver_id,
         }
     }
 
@@ -71,7 +71,9 @@ impl InputEvent {
                 event.webdriver_id = webdriver_id;
             },
             InputEvent::Touch(..) => {},
-            InputEvent::Wheel(..) => {},
+            InputEvent::Wheel(ref mut event) => {
+                event.webdriver_id = webdriver_id;
+            },
         };
 
         self
@@ -275,6 +277,17 @@ pub struct WheelDelta {
 pub struct WheelEvent {
     pub delta: WheelDelta,
     pub point: DevicePoint,
+    webdriver_id: Option<WebDriverMessageId>,
+}
+
+impl WheelEvent {
+    pub fn new(delta: WheelDelta, point: DevicePoint) -> Self {
+        WheelEvent {
+            delta,
+            point,
+            webdriver_id: None,
+        }
+    }
 }
 
 #[derive(Clone, Debug, Deserialize, Serialize)]
diff --git a/components/shared/embedder/webdriver.rs b/components/shared/embedder/webdriver.rs
index f4f9cd5d509..4333fa9fe2b 100644
--- a/components/shared/embedder/webdriver.rs
+++ b/components/shared/embedder/webdriver.rs
@@ -50,7 +50,8 @@ pub enum WebDriverCommandMsg {
         MouseButton,
         f32,
         f32,
-        WebDriverMessageId,
+        // Should never be None.
+        Option<WebDriverMessageId>,
         IpcSender<WebDriverCommandResponse>,
     ),
     /// Act as if the mouse was moved in the browsing context with the given ID.
@@ -58,11 +59,23 @@ pub enum WebDriverCommandMsg {
         WebViewId,
         f32,
         f32,
-        WebDriverMessageId,
+        // None if it's not the last `perform_pointer_move` since we only
+        // expect one response from constellation for each tick actions.
+        Option<WebDriverMessageId>,
         IpcSender<WebDriverCommandResponse>,
     ),
     /// Act as if the mouse wheel is scrolled in the browsing context given the given ID.
-    WheelScrollAction(WebViewId, f32, f32, f64, f64),
+    WheelScrollAction(
+        WebViewId,
+        f32,
+        f32,
+        f64,
+        f64,
+        // None if it's not the last `perform_wheel_scroll` since we only
+        // expect one response from constellation for each tick actions.
+        Option<WebDriverMessageId>,
+        IpcSender<WebDriverCommandResponse>,
+    ),
     /// Set the window size.
     SetWindowSize(WebViewId, DeviceIntSize, IpcSender<Size2D<f32, CSSPixel>>),
     /// Take a screenshot of the window.