Auto merge of #12813 - emilio:hit-test, r=notriddle

dom: getElementsFromPoint does the hit testing on viewport coordinates.

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We got this wrong (I think it wasn't my fault actually), I was just writing a test for #12777 when I found this.

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components/layout/query.rs

@@ -148,7 +148,9 @@ impl LayoutRPC for LayoutRPCImpl {
             let result = match rw_data.display_list {
                 None => panic!("Tried to hit test without a DisplayList"),
                 Some(ref display_list) => {
-                    display_list.hit_test(&page_point, &client_point, &rw_data.stacking_context_scroll_offsets)
+                    display_list.hit_test(&page_point,
+                                          &client_point,
+                                          &rw_data.stacking_context_scroll_offsets)
                 }
             };