components: 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: If697b7bf69b199c1796f873eedca3359cdb48c64
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2897151
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Owners-Override: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#883296}
NOKEYCHECK=True
GitOrigin-RevId: 1156b5f891de178171e71b9221a96bef1ced3d3b
diff --git a/disassembler.h b/disassembler.h
index 52c69a4..8fd5a3a 100644
--- a/disassembler.h
+++ b/disassembler.h
@@ -20,7 +20,7 @@
 // A vacuous ReferenceReader that produces no references.
 class EmptyReferenceReader : public ReferenceReader {
  public:
-  base::Optional<Reference> GetNext() override;
+  absl::optional<Reference> GetNext() override;
 };
 
 // A vacuous EmptyReferenceWriter that does not write.