[dragdrop] Add directory tree item drag drop .accepts class test

Tests that dragging a file over a directory tree item that can accept a
drop adds CSS class .accepts to that tree item.

Also: check that the drag hover causes the file-list to navigate to the
hovered tree item's directory.

Bug: 1002394
Change-Id: I4def2bfd5621b9043d615c0706cc273fc9eb16ec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2275576
Commit-Queue: Noel Gordon <noel@chromium.org>
Reviewed-by: Alex Danilo <adanilo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#784396}

chrome/browser/chromeos/file_manager/file_manager_browsertest.cc

@@ -623,6 +623,7 @@ WRAPPED_INSTANTIATE_TEST_SUITE_P(
         TestCase("transferBetweenTeamDrives").FilesNg(),
         TestCase("transferDragDropActiveLeave"),
         TestCase("transferDragDropActiveDrop"),
+        TestCase("transferDragDropTreeItemAccepts").FilesNg(),
         TestCase("transferDragAndDrop"),
         TestCase("transferDragAndHover"),
         TestCase("transferFromDownloadsToDownloads"),

ui/file_manager/integration_tests/file_manager/transfer.js

@@ -589,6 +589,60 @@ testcase.transferDragDropActiveDrop = async () => {
   await remoteCall.waitForElementLost(appId, htmlDragDropActive);
 };
 
+/**
+ * Tests that dragging a file over a directory tree item that can accept the
+ * drop changes the class of that tree item to 'accepts'.
+ */
+testcase.transferDragDropTreeItemAccepts = async () => {
+  const entries = [ENTRIES.hello, ENTRIES.photos];
+
+  // Open files app.
+  const appId = await setupAndWaitUntilReady(RootPath.DOWNLOADS, entries, []);
+
+  // The drag has to start in the file list column "name" text, otherwise it
+  // starts a drag-selection instead of a drag operation.
+  const source =
+      `#file-list li[file-name="${ENTRIES.photos.nameText}"] .entry-name`;
+
+  // Select the source file.
+  await remoteCall.waitAndClickElement(appId, source);
+
+  // Wait for the directory tree target.
+  const target = '#directory-tree [entry-label="My files"]';
+  await remoteCall.waitForElement(appId, target);
+
+  // Drag the source and hover it over the target.
+  const skipDrop = true;
+  chrome.test.assertTrue(
+      await remoteCall.callRemoteTestUtil(
+          'fakeDragAndDrop', appId, [source, target, skipDrop]),
+      'fakeDragAndDrop failed');
+
+  // Check: drag hovering should navigate the file list.
+  await remoteCall.waitUntilCurrentDirectoryIsChanged(appId, '/My files');
+
+  // Check: the target should have accepts class.
+  const willAcceptDrop = '#directory-tree [entry-label="My files"].accepts';
+  await remoteCall.waitForElement(appId, willAcceptDrop);
+
+  // Check: the target should not have denies class.
+  const willDenyDrop = '#directory-tree [entry-label="My files"].denies';
+  await remoteCall.waitForElementLost(appId, willDenyDrop);
+
+  // Send a dragleave event to the target to end drag-drop operations.
+  const dragLeave = true;
+  chrome.test.assertTrue(
+      await remoteCall.callRemoteTestUtil(
+          'fakeDragLeaveOrDrop', appId, ['#file-list', target, dragLeave]),
+      'fakeDragLeaveOrDrop failed');
+
+  // Check: the target should not have accepts class.
+  await remoteCall.waitForElementLost(appId, willAcceptDrop);
+
+  // Check: the target should not have denies class.
+  await remoteCall.waitForElementLost(appId, willDenyDrop);
+};
+
 /**
  * Tests that we can drag a file from #file-list to #directory-tree.
  * It copies the file from Downloads to Downloads/photos.