[base] CROS MemoryPressureMonitor may not wake on shutdown.

The kernel may not bubble up the close always if you don't
specify POLLIN.

BUG=chromium:964569
TESTED=tested on dev device

Change-Id: I21f54edf12a4dbec1d2b3ba5fef6c78410457338
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1715898Reviewed-by: Gabriel Charette <gab@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Brian Geffon <bgeffon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#681067}

base/memory/memory_pressure_monitor_chromeos.cc

@@ -93,7 +93,7 @@ bool WaitForMemoryPressureChanges(int available_fd) {
   base::ScopedBlockingCall scoped_blocking_call(FROM_HERE,
                                                 base::BlockingType::WILL_BLOCK);
 
-  pollfd pfd = {available_fd, POLLPRI | POLLERR, 0};
+  pollfd pfd = {available_fd, POLLPRI | POLLERR | POLLIN, 0};
   int res = HANDLE_EINTR(poll(&pfd, 1, -1));  // Wait indefinitely.
   PCHECK(res != -1);