[FilesApp] Re-enable copyBetweenWindows* browser tests in DEBUG

CL:1978684 increased the ChromeOS DEBUG bot timeout, and since that CL
FilesApp browser tests do not flake in DEBUG anymore, issue 981420.

Re-enable the FilesApp copyBetweenWindows tests that were marked flaky
on the DEBUG bots, issue 1008909.

Bug: 981420, 1008909
Change-Id: Ibb253b8aa79b093935db312448339f5feaa350f4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1983681
Auto-Submit: Noel Gordon <noel@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#728436}

chrome/browser/chromeos/file_manager/file_manager_browsertest.cc

@@ -706,14 +706,8 @@ WRAPPED_INSTANTIATE_TEST_SUITE_P(
         TestCase("openFileDialogSelectAllDisabled").WithBrowser(),
         TestCase("openMultiFileDialogSelectAllEnabled").WithBrowser()));
 
-#if defined(NDEBUG)
-#define MAYBE_CopyBetweenWindows CopyBetweenWindows
-#else
-// Flaky on Chrome OS Debug. TODO(crbug.com/1008909).
-#define MAYBE_CopyBetweenWindows DISABLED_CopyBetweenWindows
-#endif
 WRAPPED_INSTANTIATE_TEST_SUITE_P(
-    MAYBE_CopyBetweenWindows, /* copy_between_windows.js */
+    CopyBetweenWindows, /* copy_between_windows.js */
     FilesAppBrowserTest,
     ::testing::Values(TestCase("copyBetweenWindowsLocalToDrive"),
                       TestCase("copyBetweenWindowsLocalToUsb"),