Disable base::DirReaderPosixUnittest::Read on clang ASAN.

The test harness has working directory /, which is not readable in
this test.

Bug: 804348
TBR: aberent@chromium.org,brettw@chromium.org,thestig@chromium.org
Change-Id: I31f02bef8aa61f62e2e07c94279e875d8b6d9570
Reviewed-on: https://chromium-review.googlesource.com/891158Reviewed-by: Matthew Cary <mattcary@chromium.org>
Commit-Queue: Matthew Cary <mattcary@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532391}

base/files/dir_reader_posix_unittest.cc

@@ -21,7 +21,14 @@
 
 namespace base {
 
-TEST(DirReaderPosixUnittest, Read) {
+#if defined(ADDRESS_SANITIZER)
+// On ASAN builds, the working directory for the test is /, which is not
+// readable. See crbug.com/804348.
+#define MAYBE_Read DISABLED_Read
+#else
+#define MAYBE_Read Read
+#endif  // defined(ADDRESS_SANITIZER)
+TEST(DirReaderPosixUnittest, MAYBE_Read) {
   static const unsigned kNumFiles = 100;
 
   if (DirReaderPosix::IsFallback())