Revert "Add FDIO_EVT_PEER_CLOSED to WatchFileDescriptor(WATCH_READ) events."

This reverts commit f130981c.

Reason for revert: Doesn't actually fix anything. >.<

Original change's description:
> Add FDIO_EVT_PEER_CLOSED to WatchFileDescriptor(WATCH_READ) events.
> 
> WatchFileDescriptor(WATCH_READ) should result in
> OnFileCanReadWithoutBlocking() if the descriptor is at end-of-stream
> when it is invoked, to wake the caller to detect that by attempting to
> read and receiving zero bytes.
> 
> Bug: 898938, 706592, 884299
> Change-Id: I77662fe77eb8fb988089640a75a60d470770b78f
> Reviewed-on: https://chromium-review.googlesource.com/c/1316672
> Commit-Queue: Wez <wez@chromium.org>
> Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#605154}

TBR=wez@chromium.org,sergeyu@chromium.org,fdegans@chromium.org

Change-Id: I1a98ece4b90de54c2c789dee64c226eb92bcda38
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 898938, 706592, 884299
Reviewed-on: https://chromium-review.googlesource.com/c/1316675Reviewed-by: Wez <wez@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605157}

base/message_loop/message_pump_fuchsia.cc

@@ -125,7 +125,7 @@ void MessagePumpFuchsia::FdWatchController::OnZxHandleSignalled(
   bool* was_stopped = was_stopped_;
   if (events & FDIO_EVT_WRITABLE)
     watcher_->OnFileCanWriteWithoutBlocking(fd_);
-  if (!*was_stopped && (events & (FDIO_EVT_READABLE | FDIO_EVT_PEER_CLOSED)))
+  if (!*was_stopped && (events & FDIO_EVT_READABLE))
     watcher_->OnFileCanReadWithoutBlocking(fd_);
 
   // Don't add additional work here without checking |*was_stopped_| again.
@@ -192,14 +192,13 @@ bool MessagePumpFuchsia::WatchFileDescriptor(int fd,
 
   switch (mode) {
     case WATCH_READ:
-      controller->desired_events_ = FDIO_EVT_READABLE | FDIO_EVT_PEER_CLOSED;
+      controller->desired_events_ = FDIO_EVT_READABLE;
       break;
     case WATCH_WRITE:
       controller->desired_events_ = FDIO_EVT_WRITABLE;
       break;
     case WATCH_READ_WRITE:
-      controller->desired_events_ =
-          FDIO_EVT_READABLE | FDIO_EVT_PEER_CLOSED | FDIO_EVT_WRITABLE;
+      controller->desired_events_ = FDIO_EVT_READABLE | FDIO_EVT_WRITABLE;
       break;
     default:
       NOTREACHED() << "unexpected mode: " << mode;