DirReaderLinux: Don't crash if the directory is deleted

If Next() is called but the directory has been deleted, debug builds
just crash. Instead, don't crash because this is normal behavior,
especially for reading /proc/<pid> directories that can disappear
any time a process dies.

Change-Id: If110ca05d576b205ba4113fa13d0f8e044beaf6a
Bug: 1493493
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4961577
Commit-Queue: Lei Zhang <thestig@chromium.org>
Commit-Queue: Matthew Denton <mpdenton@chromium.org>
Auto-Submit: Matthew Denton <mpdenton@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1213066}

base/files/dir_reader_linux.h

@@ -65,7 +65,9 @@ class DirReaderLinux {
     if (r == 0)
       return false;
     if (r < 0) {
-      DPLOG(FATAL) << "getdents64 failed";
+      if (errno != ENOENT) {
+        DPLOG(FATAL) << "getdents64 failed";
+      }
       return false;
     }
     size_ = static_cast<size_t>(r);