chromeos: Replace base::Optional and friends with absl counterparts

This replaces:
- base::Optional -> absl::optional
- include "base/optional.h"
  ->
  include "third_party/abseil-cpp/absl/types/optional.h"
- base::nullopt -> absl::nullopt
- base::make_optional -> absl::make_optional

Bug: 1202909
Change-Id: I4259c20a7214da46e0e0a9da4aace5fd3606a8b9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2897223
Auto-Submit: Anton Bikineev <[email protected]>
Commit-Queue: Peter Kasting <[email protected]>
Reviewed-by: Peter Kasting <[email protected]>
Owners-Override: Peter Kasting <[email protected]>
Cr-Commit-Position: refs/heads/master@{#883280}
diff --git a/chromeos/components/proximity_auth/proximity_auth_system.h b/chromeos/components/proximity_auth/proximity_auth_system.h
index a67b0ded..bdc3097 100644
--- a/chromeos/components/proximity_auth/proximity_auth_system.h
+++ b/chromeos/components/proximity_auth/proximity_auth_system.h
@@ -54,7 +54,7 @@
   void SetRemoteDevicesForUser(
       const AccountId& account_id,
       const chromeos::multidevice::RemoteDeviceRefList& remote_devices,
-      base::Optional<chromeos::multidevice::RemoteDeviceRef> local_device);
+      absl::optional<chromeos::multidevice::RemoteDeviceRef> local_device);
 
   // Returns the RemoteDevices registered for |account_id|. Returns an empty
   // list
@@ -88,7 +88,7 @@
   // Exposed for testing.
   virtual std::unique_ptr<RemoteDeviceLifeCycle> CreateRemoteDeviceLifeCycle(
       chromeos::multidevice::RemoteDeviceRef remote_device,
-      base::Optional<chromeos::multidevice::RemoteDeviceRef> local_device);
+      absl::optional<chromeos::multidevice::RemoteDeviceRef> local_device);
 
   // ScreenlockBridge::Observer:
   void OnScreenDidLock(