chrome: 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
AX-Relnotes: n/a.
Change-Id: If011b89bfb5f3561e152aeee242b0b2fe1ab4587
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2897520
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@{#883266}
diff --git a/chrome/browser/ui/browser_live_tab_context.h b/chrome/browser/ui/browser_live_tab_context.h
index 90663a3..1e7123d 100644
--- a/chrome/browser/ui/browser_live_tab_context.h
+++ b/chrome/browser/ui/browser_live_tab_context.h
@@ -43,7 +43,7 @@
   sessions::LiveTab* GetLiveTabAt(int index) const override;
   sessions::LiveTab* GetActiveLiveTab() const override;
   bool IsTabPinned(int index) const override;
-  base::Optional<tab_groups::TabGroupId> GetTabGroupForTab(
+  absl::optional<tab_groups::TabGroupId> GetTabGroupForTab(
       int index) const override;
   const tab_groups::TabGroupVisualData* GetVisualDataForGroup(
       const tab_groups::TabGroupId& group) const override;
@@ -59,7 +59,7 @@
       int tab_index,
       int selected_navigation,
       const std::string& extension_app_id,
-      base::Optional<tab_groups::TabGroupId> group,
+      absl::optional<tab_groups::TabGroupId> group,
       const tab_groups::TabGroupVisualData& group_visual_data,
       bool select,
       bool pin,
@@ -68,7 +68,7 @@
       const SessionID* tab_id) override;
   sessions::LiveTab* ReplaceRestoredTab(
       const std::vector<sessions::SerializedNavigationEntry>& navigations,
-      base::Optional<tab_groups::TabGroupId> group,
+      absl::optional<tab_groups::TabGroupId> group,
       int selected_navigation,
       const std::string& extension_app_id,
       const sessions::PlatformSpecificTabData* tab_platform_data,