[Extensions] Re-enable a fileSystem API test.

FileSystemApiOpenExistingFileWithWriteTest was disabled as flaky
long ago, but it passed on the bots with flying color on 3000
iterations.

Bug: 177163
Change-Id: Icfa48575d2c557afc9d4ce6ec8fb6a402a84ae82
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2173399Reviewed-by: Istiaque Ahmed <lazyboy@chromium.org>
Commit-Queue: David Bertoni <dbertoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#766463}

chrome/browser/extensions/api/file_system/file_system_apitest.cc

@@ -433,14 +433,8 @@ IN_PROC_BROWSER_TEST_F(FileSystemApiTest,
   CheckStoredDirectoryMatches(base::FilePath());
 }
 
-// http://crbug.com/177163
-#if defined(OS_WIN) && !defined(NDEBUG)
-#define MAYBE_FileSystemApiOpenExistingFileWithWriteTest DISABLED_FileSystemApiOpenExistingFileWithWriteTest
-#else
-#define MAYBE_FileSystemApiOpenExistingFileWithWriteTest FileSystemApiOpenExistingFileWithWriteTest
-#endif
 IN_PROC_BROWSER_TEST_F(FileSystemApiTest,
-    MAYBE_FileSystemApiOpenExistingFileWithWriteTest) {
+                       FileSystemApiOpenExistingFileWithWriteTest) {
   base::FilePath test_file = TempFilePath("open_existing.txt", true);
   ASSERT_FALSE(test_file.empty());
   FileSystemChooseEntryFunction::SkipPickerAndAlwaysSelectPathForTest(