[Interop] Deflake pointerevent_click_during_capture.html

The test has been flaking for the auxclick action where the
middle-click drag is probably causing autoscroll in some platforms.

This CL changes the action to use the right mouse button instead, after
suppressing any context menu invocation.

Bug: 40851596
Change-Id: I4e36b3aceb75d5edcbd0c9599ada9f7af9ef7b78
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5873347
Commit-Queue: Mustaq Ahmed <mustaq@chromium.org>
Reviewed-by: Kevin Ellis <kevers@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1358971}

pointerevents/pointerevent_click_during_capture.html

@@ -64,13 +64,15 @@
       target.addEventListener(ename, logEvent);
     });
   });
+  // Suppress context-menus at right-clicks.
+  parent.addEventListener("contextmenu", e => e.preventDefault());
 
   function dragBetweenChildrenAndClickOnDone(from_child, to_child, test) {
     let actions_promise = new test_driver.Actions();
 
     const button_type = (event_to_test === "click")
         ? actions_promise.ButtonType.LEFT
-        : actions_promise.ButtonType.MIDDLE;
+        : actions_promise.ButtonType.RIGHT;
 
     actions_promise.addPointer(test_pointer, pointer_type)
       .pointerMove(0, 0, {origin:from_child})