Remove webkitdropzone.

third_party/WebKit/LayoutTests/fast/dnd/resources/dropEffect-common.js

+const mouseMoveToCenter = element => {
+  const clientRect = element.getBoundingClientRect();
+  const centerX = (clientRect.left + clientRect.right) / 2;
+  const centerY = (clientRect.top + clientRect.bottom) / 2;
+  eventSender.mouseMoveTo(centerX, centerY);
+};
+
+const dropEffectTest = params => {
+  promise_test(t => {
+    document.querySelector('.test-description').textContent =
+        JSON.stringify(params);
+
+    const dragged = document.querySelector('.dragged');
+    if (dragged && !dragged.classList.contains('no-ondragstart')) {
+      dragged.ondragstart = t.step_func(event => {
+        event.dataTransfer.setData('text/plain', 'Needed to work in Firefox');

[jsbell, 2017/03/02 22:06:45]

Happen to have a link to a bug?

[pwnall, 2017/03/02 22:34:29]

I've been cargo-culting this from other tests around here.

I'll go research.

+        if ('allowed' in params)
+          event.dataTransfer.effectAllowed = params.allowed;
+      });
+    }
+
+    const dropZone = document.querySelector('.dropzone');
+    dropZone.ondragover = t.step_func(event => {
+      event.preventDefault();
+      if ('drop' in params)
+        event.dataTransfer.dropEffect = params.drop;
+    });
+    let gotDrop = false;
+    dropZone.ondrop = t.step_func(event => {
+      event.preventDefault();
+      gotDrop = true;
+    });
+
+    return new Promise((resolve, reject) => {

[jsbell, 2017/03/02 22:06:45]

Nit: Move this up to the top of the `t => {` block so that if anything above
throws it turns into a promise rejection. Could then also be just:

t => new Promise((resolve, reject) => {
...
}.then(...)

[pwnall, 2017/03/02 22:34:29]

Done.

+      const doneButton = document.querySelector('.done');
+
+      if (dragged) {
+        dragged.ondragend = t.step_func(event => {
+          resolve(event.dataTransfer.dropEffect);
+        });
+      } else {
+        doneButton.onclick = t.step_func(() => {
+          resolve('none');
+        });
+      }
+
+      if (window.eventSender) {
+        if (dragged) {
+          mouseMoveToCenter(dragged);
+          eventSender.mouseDown();
+        } else {
+          eventSender.mouseMoveTo(0, 0);
+          eventSender.beginDragWithFiles(['resources/dragged-file.txt']);
+        }
+        setTimeout(() => {
+          mouseMoveToCenter(dropZone);
+          eventSender.mouseUp();
+          if (doneButton) {
+            setTimeout(() => {
+              const clickEvent = new Event('click');
+              doneButton.dispatchEvent(clickEvent);
+            }, 100);
+          }
+        }, 100);
+      }
+    }).then((dragOperation) => {

[jsbell, 2017/03/02 22:06:45]

nit: no () needed

[pwnall, 2017/03/02 22:34:29]

Done.

+      if ('operation' in params) {
+        assert_true(gotDrop, 'drop target should have received a drop event');
+        assert_equals(dragOperation, params.operation);
+      } else {
+        assert_true(
+            !gotDrop, 'drop target should not have received a drop event');
+        assert_equals(dragOperation, 'none');
+      }
+    });
+  }, `effectAllowed: ${params.allowed} dropEffect: ${params.drop}`);
+};